Why does my advisor / professor discourage all collaboration?
This sounds pretty extreme, even for the &quot;sink or swim&quot; school of education. If you can meet the extreme standard without going crazy you will probably turn out ok, if a bit of a workaholic. But the road will be hard and painful.
But, given your sense of it, you should probably move quickly to the exits. Not everyone is like that. Some of us actually try to be supportive.

As for the &quot;why&quot; of it, he just seems to demand perfection and won't compromise in any way.