>>no one can make any peripheral or add on

Actually, that's not exactly historically correct.

I never bought one, but I fell in love with the Apple II before the IBM PC came along and stole my heart.
Part of its appeal was its use of the centronics (now the parallel) interface which allowed someone to plug in any printer using that interface.
We take the open interface for granted now, but it was a big deal then and the IBM PC emulated it.