Tactical Systems are Tacky
A vision came to me of a perfectly tactical RPG system, and then I realized it was worthless, because tactical RPGs are tacky.
This perfectly tactical system could be memorized in minutes, and let you play without any board or counters. Skilled players would do well, unskilled players would do badly. Players would represent stats and equipment with little boons and penalties to the system, letting someone with less skill gain an upper hand, but only a little. Supremely skilled players would still win against someone with better stats, because perfectly tactical systems have do not use luck.
If I ran a game with this system, I could ensure the NPCs win every time, even with worse equipment, because I know how to do tactics. I can calculate moves in my head, add numbers, and remember short sequences on the fly. The players wouldn't stand a chance.
...and I've locked myself out of GMing. Maybe I could 'let' the players win some times, but that would be hollow, and patronizing. I much preferred letting people come up with ideas, and letting the dice decide which ideas work.
But I could find another GM - someone less capable of doing rote calculations in their head, who doesn't care about chess opening moves - they could run a more impartial game. I could play a character in that game, and I'd win all the time. Others would win some of the time, and players who don't play games often wouldn't be able to do shit. They'd step up, get stabbed by a goblin, and have to make their fourth character for the session, because they don't do tactics. And in a purely tactical game, nobody does well, unless they do tactics.
So the people in my group who liked making a fighter and swinging a sword, or coming up with crazy ideas about chucking chairs, or what they can set fire to? They can't play fighters any more. Of course, the system can represent all of those things, and give them bonuses for the items or whatever. But if they can't think with tactics, then they will still lose every fight. And the game will feel like playing chess against a grand master, with a fantasy narrative smeared over the top.
All RPGs are Tactical
Give a Mathematician any system - any game, or shopping list, or other well-defined objective, and they can show the perfect way to play the game, or how to optimize buying things. Some RPGs may seem like they have 'a lot' in the way of tactics, but they really just have long lists of things to do. Once you take a look at what an individual character can do, calculating the optimal move becomes trivial ('trivial' is a Maths-word which means 'I could do it if I wanted to but I don't').
The World of Darkness games may seem to have tactics, because you can elect to a 'headshot' by taking a +3 difficulty, in return for +2 Damage dice; but the Maths shows that you should never take this move when you have a dice pool greater than 3, and always take this move otherwise. D&D iterations with special Feats for fighters may seem to have tactics, but the correct answer is almost always to use the most powerful attack you have against the biggest creature, then vanish. The various 'build systems' which seek to make optimized characters are indeed tactical, but each 'move' only occurs when the character gains new abilities; this makes the campaign 'tactical', but not the weekly game session.
Nobody can design around this - every game, every activity, every system (in every sense) remains vulnerable to pedantic Mathematicians; and every new rule the designer creates lead to more potential for sneaky Mathematicians to raise their chances of success above the average. RPG designers can't solve problem with a pure Snakes and Ladders approach - the system exists to represent every meaningful facet of a world, so they must adjust the dice in some places, but not others, and every new rule means a new opportunity for pedantic Mathematicians. The real challenge is not in making a 'tactical game', but in avoiding tactics as much as possible.
Cracks in the Rules are Fun
When D&D's 3rd edition came out, the designers wanted to avoid anyone running up to an opponent, making an attack, then running away, so they created the 'attack of opportunity'. But the fix just made more problems: getting an 'attack of opportunity' is good, so everyone would have the incentive to maximize their chances of getting one, and might end up making 10 attacks in a single round, if they can somehow force 10 people to move towards them or past them.
The rules for making an 'attack of opportunity' grew and grew to adjust to 'tactical' abuses, becoming more abstract with each layer. And players enjoyed finding those cracks in the system, and exploiting them.
That's a great part of the game - when you figure out that Magic Missile will let your character detect invisible walls, or use a Cure Wounds spell as a makeshift Detect Undead spell by casting it on a suspected vampire.
No Prize is Too Small
Players who enjoy finding these little exploitable cracks in the system will enjoy the experience no matter how small the prize. Using Cure Light Wounds to find out if someone is a vampire won't be very useful most of the time, but players will still feel happy with the result, even if they use it only once.
And if someone stews over numbers all night, and figures out how to get +10% average Damage with a particular weapon and combat manoeuvre, or how to add a +5% chance to hit small creatures, just by moving once every two turns, or a +2% Damage average by performing the YMCA before battle...if that player finds some advantage, then they will be happy with the solution, even with small gains. They will feel happy with their +2% accuracy Bonus because that means the character has been optimized, and it also means that player is a very clever person, and they can help the rest of the party with their hard-earned conclusions.
Back to the Start
RPG system designers should never facilitate tactical play, or any use of tactics. Instead, they should minimize the potential for tactics at every turn, because tactical play is inevitable, and worthless.
'Tactics' are great fun for players and GMs, but game designers should eliminate them as far as they can (while knowing they will fail to eliminate them).