I have to disagree with you on points 1-3. They are the minor points. I think number 4 should be on top of your list. Number 4 and then number 3 together probably make up 90% of the real reason why people end up doing a phd.
Perhaps. But the minor points are the ones most Ph.D's will say are their reasons. The last one (social/psychological) is probably the least likely to be admitted.
1) It's the only way to get a job in certain really interesting fields
2) Ph.D's garner massive respect from peers
3) Disrespect for industry, there's a perception of tedium, and looking down on people who are "code monkeys" or "project managers"
4) Some kind of academic momentum - it's socially and psychologically easier to stay in college/academia than to switch to industry