Why does it say some do not need to do an interview for I-485 adjust status but some need to?

Question

I saw on a website some cases recieve an approval letter and don't need to go to an immigration interview but yet others need to. Why?

Answer 1

Family based applications for AOS usually require interviews as a means to prove the validity of the relationship. Recently, though, some applications have been forwarded to be processed in California if they are straightforward. Many of those lucky applicants are not asked for interview but are simply approved.

Answer 2

Many of employment based immigration don't require an interview, because the US employer is the petitioner. Once US employer is proved to be legit business and ability to pay the lawful salary, the beneficiary will get green card granted. Well established business doesn't change the venue suddenly. Most of family based immigration requires an interview, because the people's relation can change in even short time.