There are two big advantages to using a 3rd party system.

1) There are a lot of cases where aggregated user data, even if anonymized, allows for insights that you can't get using just your own data.

2) The software is really just a stand in for a process. A way of doing something, like record keeping or tax filing, etc. A lot of times it makes sense to follow an already established process rather than creating your own. You are less likely to encounter unexpected pitfalls that way.

I don't see how you can overcome those just by having an AI that can build simple crud apps at will.