Why do companies look for people they know privately instead of advertising for jobs? Everybody help me analyze it.

All the situations mentioned above are relatively easy to happen.

The most important thing is the "cheat scheme". In view of this possibility, we cannot rush to conclude that they are fraudulent companies. Make unannounced visits to learn the details of the company. Legal representative, whether to register, where to register, online comparison of registration codes, how big the company is, and so on. It's not too late to hand in the plan when everything is clear.

Besides, do they?

(of a candidate for a position) be nominated before fulfilling the prescribed procedures.

This situation is basically obvious. Since it is introduced by a friend, we can start with friends and explore the news.

There is a more positive possibility. I don't know if you have thought about it. Nowadays, many companies prefer not to recruit people from outside, but also to adopt the "relatives first" approach. Will this be another good opportunity?

I suggest thinking back and forth more.