I'd say REGULAR is probably the most pure of difficulties. No scripting, freer animations, more unpredictable and balanced. From professional onwards, the scripting and rigidity begins. Only when you play on regular after a few games on professional, will you realise how free regular is.
You are right and i agree, but on regular it's really too easy to win and and becomes useless for many people.
So you are forced to play at higher difficulty.
I found the best gameplay (no scripting) playing friendly matches on professional.