Interviewing - as others pointed out, going through the interview rounds can be exceedingly and unnecessarily daunting and stressful since, as an employee, there's a massive imbalance in power between yourself and your potential employer.
Inertia - things are good so far, why upset the apple cart? They could be better, but not without initial (or long term) headaches: adjusting to a new culture, new colleagues and management, different rules, re-establishing social boundaries etc.
Remuneration: OK money, better than being a nurse, a teacher and plenty other, more useful and more important jobs than mine. So it's mixture of gratefulness and other, not so positive feelings.
Financial stability: being employed and doing something I know how to do well beats being a freelancer in terms of regular income, especially since I'm not great at finding clients and doing business. They require different skills and it's one of the main reasons many brilliant people (which I most certainly am not) can't start their own thing: being an excellent engineer / scientist / writer / carpenter doesn't make you good or patient enough with people in order to actually do business.
Some degree of freedom: my employer doesn't measure every aspect of my work or transforms social relations into KPIs (a dystopic thing, to say the least), doesn't actively spy on me and, because I work from home on my own machine, I don't need to go through an infantilisation process whereby I have to ask IT Dep to update a piece of software or install something new just because I want to try it. You know, like an adult should be able to. Say what you will about risks, they are all observed from the business' perspective; I find it extremely difficult and infantilising to accept that I am unable to control my own machine and everyday tools because the business can't cope with risks. My needs as a human being should not come after the needs of the business, because the only reason we have businesses is to make life better for human beings.
Changing jobs right now would mean navigating - yet again! - this complex reality where one is forced to research, apply, seduce, negotiate and maintain professional relationships. Which I'll have to do anyway sooner or later.