In a conventional language you have to decide when something gets evaluated, and whether to cache the value or recompute it every time. These decisions get baked into your code early on because the control and data flow are intertwingled.

In Haskell you just specify the data flow and the compiler looks after the control flow. Sometimes the compiler's default idea is less than optimal, so you can tweak it by adding bangs and other strictness annotations to the code. The semantics change slightly because maybe now you evaluate an expression that throws an exception or goes into an endless loop, whereas before it wasn't evaluated, but apart from that the changes are guaranteed not to affect the meaning of your code.

Sure, garbage collected languages are not suitable for hard real time, but interactive apps and games are soft real time (a 100 ms delay once per hour isn't going to break the game). GHC is already there.