No-castling variant is a thing. It generally makes taking the King to safety more difficult, encouraging a more aggressive style (in the spirit of "I'll get to

No-castling variant is a thing. It generally makes taking the King to safety more difficult, encouraging a more aggressive style (in the spirit of "I'll get to yours before you get to mine"). Kramnik revived the idea during his collaboration with DeepMind (where he tested several chess variants, revolving around only minor, albeit impactful adjustments to the ruleset). One potential problem with no castling is that players may end up castling "manually", which takes several moves and becomes a mundane "housekeeping" task, actually sucking some dynamics out of the game. That was probably the reason why it was invented in the first place, to sort of automate the obvious thing away. By the way, European chess added much more to the original version beyond just castling. The Queen would originally move in the same manner as the King (only by one square), the "mad Queen" thing is a European invention. So is the pawns' ability to move forward by 2 squares from their initial position. (And I'm guessing the incentive for that was of similar nature as above - to speed the game up).