I think a lot of times people aren't entirely honesty with their employers as to why they are leaving when they resign. That's why you see physicians and HR attribute salary as the number 1 reason they think people leave, when most NP's say it's stress as their number one reason. A lot of times it's both. How many people here have posted about leaving a stressful job on here and also ending up making more? I know I'm one of them.
When I left my first NP job fulltime, it was mostly because the office environment was so toxic, specifically the manager (physician spouse) treatment of the MA's, that I hated being there. I loved my boss and he treated me well, but it really bothered me seeing hard working kids be treated like scraps. When it came time to leaving, I didn't want to tell my boss I was leaving because his practice environment was too stressful and toxic, I told him it was purely monetary and put the number I was leaving for a lot higher than he I knew he would be willing to pay to avoid a counter offer (even though it wasn't that actual figure). It worked out well because I ended up going to work for a large hospital corporation for a better salary, but vastly superior benefits package, and now my boss is a nursing administrator that lets me do my own thing with minimal oversite. I also have a very cordial relationship with my previous boss and still do work on the side for him. Had I expressed how much I hated his office practice and how his wife managed it, I would likely have burned some significant bridges in a medical community where word travels fast.
Overall, I think what we give as our official reason for leaving a company is usually just the surface of a multi-faceted decision.