I think it’s a combination of a few behaviors: Developers have this “if I can do it myself albeit in 10 times more time I won’t pay for the service even if it doesn’t make any financial sense whatsoever” and “This is cool but requires investment of my time while not providing way out of they start to suck or disappear” and “this is clever but what I need is help with the boring bits” mentality.

The stuff most developers are comfortable paying for is things like hosting, tools that do something the developers find very boring or have no domain overlap and don’t have viable free alternative.

“Why would I pay 9.99 if I can set up a free alternative in a few days and host it myself for 4.99? If I can’t host it myself I don’t trust you anyway”