In my experience, recommendations aren't very common in programming, unless you're talking about referrals by former supervisors/colleagues to some job opening.
Recommendations really only come into play when you're talking about the best engineers. In which case, you're effectively no longer interviewing, just getting people in your network who say they must hire you or tell other people in their networks they must hire you.
Related, in blog form: https://www.joelonsoftware.com/2006/09/06/finding-great-deve...