Because not being normal results in being lonely, rejected by society, and often unable to keep a decent job. After a lifetime of struggling just to achieve fairly pitiful social success, I would give a great deal to be able to be normal.

This to me reads as someone who has never been "the bad kind of unique". Not being normal carries very heavy practical repercussions in some cases.

"Just be yourself" is only good advice for people whose 'self' is acceptable and well-functioning.

I never got the sense the author was trying to push people or himself into a box, more that he wanted to be able to connect to others more easily.