This is because software in contrast to games is usually meant to get shit done with the least possible friction.

While experimentation will always have a driving force, standardization allows a program to lower the barrier of usage to everyone. Especially to those who are not a typical HN user but rather like your stereotypical parents.

Games are not about getting stuff done, so people enjoy learning how it works, which in its own way reduces friction.

Also as a player: I'd love more consistency. Especially on mobile - the impossibly vast array of same-but-different is wearying, not interesting.

You're right but I've always thought it's a bit sad how many hours must be spent recreating the same similar assets - concrete, grass, clothes, etc. - just so people don't have this clinical moment where they recognise something from another game.

In view of games as art, these are definitely mandatory stylistic choices involved in creating a unique experience for the players.