All the time. Let me give you an example from a game I made. During early R&D I used 32 bit numbers and a fixed point of 11 bits. That means that a normalized vector is between 1024 and -1023. You can do 2 dot products between vectors before it breaks it breaks. (10 + 10 + 10 bits plus one sign bit). That means that you have to do a lot of shifting down. the world can only be 20 bits large, because you need to be able to multiply world coordinates with vectors without getting overflow.
20 bis is very low resolution for a real-time world. You get problems with things not being able to move slow enough at high frame rates. (this was in 2D). Switching to 64 bit was the right move.
> some game engines
and
> simple games
A 3D game is not a simple game.
> the approximation is generally good enough for a game
No, it's not generally good enough for a game – only for some games, and not good enough for any game with 3D graphics.
Using fixed point with 11 bits after the decimal, with numbers as low as 100 (18 bits) we already have errors as large as 100·(1/100)=0.977.
If you try to do with Fixed Point Arithmetic what was intended to be done with Floating Point, you're the problem.
A 32 bits integer can hold values up to 4 billions, if I have that kind of value in a simple game, then yes i will switch to Floating Point Arithmetic, but when does that use case happen if you're not writing a physic simulation game ?