this is largely my experience, usually I leave because I hear of others at my "level" that are earning more and I start to believe that the company I am at has

this is largely my experience, usually I leave because I hear of others at my "level" that are earning more and I start to believe that the company I am at has fallen behind, then I ask for a raise, they don't give it to me and I leave for more money. rinse, repeat. I am underpaid at the moment but what's keeping me around is I get to do what I want and there is not the pressure I had elsewhere.