most fighting games are designed really for the competitive multiplayer experience really.
With playing against computers though, writing good AI that is both challenging but still do-able is really hard. Let's not forget different players have different levels of skill so you need to make sure that the end level boss has to be adjustable in terms of difficulty.
When you're playing single player, the experience is totally different from multiplayer. In single player, you're looking for two things. 1. Holes in the AI you can exploit and 2. combos. The first one is trying to spot patterns and moves that leaves openings. while the second part is where you practice practice and practice muscle memory. Beyond that, there is really not much you can do in single player mode. You can't do things like a 50/50 mixup because the computer will read through it every single time. You can't do things like corner trap set up because again, the computer will probably just break the trap every single time with perfect execution. That or the comp will fall for it every single time, rendering the entire challenge too easy.
And also, in single player mode, there is no such thing as high risk, high reward gambits. That just doesn't happen, as the AI will either 1. fall for it every single time, making it not a gamble but just a trained response or 2. never fall for it and interrupt your move before it can finish.
So a lot of the interesting things you can do in fighting games you pretty much have to save for the multiplayer portion.
BlazBlue (and it's predecessor Guilty Gear) have the distinction of being insanely hard to learn too, which makes me never want to touch the stuff.
