Yes the design is all for fast assembly, either you push on and it never is removed, or it is screwed on and makes it's own threads, or it is screwed on a thread, and self locks, or is pushed onto a thread and it self tightens with a half turn only. Removal is in most cases not considered at all, only for the last type, where the advantage over a nut is integrated washer, and light mass, so saving both 5 seconds during assembly, and 2g in mass, so you can come in under the design mass, and get that bonus.