I've run in to this myself as a tech contractor, not just in moving between companies but in trying to move between contracting agencies. Despite not being legally binding in my state, other agencies won't touch you until you've spent half a year scraping by on unemployment. They really make sure you've learned your lesson about wanting better for yourself.
I worked on several iterations of a triple-A game franchise. One of my friends there was a very talented 3d artist who had worked in that studio, on that title, since the very first. He knew the tools, the processes, the people, the studio culture and had technical skills they absolutely needed. When he was negotiating to come back for the 4th entry in the series, he had to accept a $5/hr pay cut to keep working. That's how we're rewarded for dedication and expertise now.
But hey, free soda in the breakroom!