It costs more than it is worth to have them do better. As a framer is takes me a couple minutes more to compensate. To have the do it would take hours of labor.
I presume you're talking about scribing the bottom plate, or perhaps another board placed between the foundation and the bottom plate? Why couldn't a layer of that same sort of scribed board be placed on the foundation before placing the prefab modules?
Depends on where it was. The worst case I saw was a half wall, so we cut each stud a different length.
There are options for prefab as you saw - but when building on site we have the saws and other tools needed anyway, so it isn't a big deal to use them. With prefab they don't normally use those tools so you have to account for the cost of getting them out putting them away.
"What do you mean you didn't finish all the tickets in this sprint? Must be shoddy work."
You're looking at single pieces of a complex and already optimized-for-several-factors system and assuming it would be trivial to do it better for one factor without taking others into account...
