IME, yes people are hesitant to leave sometimes out of a fear of the interview process, but I think this is no different than other industries where people generally are hesitant to take action that has a chance of of 0 payoff with a lot of upfront investment.

I don't think that's unique to software engineering, and I don't think its more pronounced in our industry.

The standard tenure of most engineers is about 3 - 5 years, a very short amount of time. People try and leave all the time. How long it takes someone to leave is likely a good proxy for their risk aversiveness. But people do switch a lot.