Why are there points of no return?
The points at which the game transition between acts seem a bit arbitrary (mainly for Act I to Act II), and I don’t see a narrative or mechanical reason to lock us out of previous maps and quests. As far as I remember, previous Baldur’s Gate games didn’t have this kind of points of no return. Why do you think they did it? Do you like it?
There isn’t a point of no return between A1 and A2. Rather, you need to do certain A1 events prior to A2 or those events resolve without you (e.g. Goblin Attack, several others).
You can travel back to A1 while in A2. Only A3 prevents back-travel, and that’s for well-established story reasons.
I generally prefer having control of the timing rather than having it being tied to X amount of rests or something (notable exceptions for certain quests existing, of course).
You do get locked out of traveling back to Act 1 areas some time in Act 2. I think once you enter the Temple of Shar?
I wanted to go back for another crack at the forge and I couldn’t.
Alendi