Unity: We need more funding for engine development, therefore we will unilaterally increase fees and start charging per installation, or you can be exempt from that if you lock yourself into our advertising platform, and it's not like you can really switch to a competitor anyway

Godot: We need more funding for engine development, therefore we will cut out the donation processing middleman so that we get to keep more of your contribution, and do an additional funding drive for those who can afford it, but don't worry if you can't contribute!

I don't know, but if I were a game developer, I'd certainly be developing some Opinions around engine choices and sustainability right about now