Select circuit transfer switch vs. Interlock kit

Hello fellow electricians, I am one of you now!
**Warning**This will probably be a long winded post for a simple question.
My father asked me to set him up with a generator in case of power outage, so I told him my favorite way to do this is with a back feed breaker / interlock kit. Because I just recently got my Masters license and am looking to potentially start targeting work in their area (Northern NH) I decided to call a few electricians just for s**ts +gigs and see what it would cost him/ what the time line would be. I called 6 companies before I finally got someone on the line and explained to them what I wanted done. I was playing dumb and I am sure most of you reading this will hate that, I am sure I would but I had to do it. Anyway getting to the point, the guy tells me that his company does not install interlocks and that I could probably find some other turkey to do it for me but we don't do that here. I called for pricing but was thrown off by him ultimately calli...