Paid version have that problem somewhat less because they have a source of income that could dry up if they do. Paying someone means they are beholden to you as well, while free gives you nothing.

There is a reason I get my email via fastmail: they differentiate themselves on privacy features. I also have my own domain, so if fastmail does turn evil they know I can easially move away. I can run my own email server, but having done that I know it is harder than I want. There are other services I'd pay for if I could find someone I could trust to take a small amount of money. (small is key - plenty would do this for thousands, but I don't have that much free cash)

Don't get me wrong, the above is not very large, but it is still something.