I believe there is a more to this than you are considering. Just spinning something up can often be a quick fix which ends up as a time drain down the road. These tools tend to start out very simple, but over time the scope grows, like with all systems and before you know it your back-office software is spaghetti code, outdated, full of bugs and security vulnerabilities.
Considering that these tools often get the lowest priority, since they are used by only a handful of people to do administrative tasks, no dev wants to put up their hand to write some curd app as a side project which has the most access to cross account sensitive data. And even less so do companies want to hear that they need to allocate more resources to something that does not directly benefit customers.
Then there is also knowledge transfer. These tools are flexible enough to build useful things, but usually in a very structured way. By enforcing this, new devs which need to change something in the app can do it right away without breaking stuff. Try to do this on some custom app someone wrote long ago and has since left the company, and it will likely end with - I think we need to rewrite this thing...
Considering that these tools often get the lowest priority, since they are used by only a handful of people to do administrative tasks, no dev wants to put up their hand to write some curd app as a side project which has the most access to cross account sensitive data. And even less so do companies want to hear that they need to allocate more resources to something that does not directly benefit customers.
Then there is also knowledge transfer. These tools are flexible enough to build useful things, but usually in a very structured way. By enforcing this, new devs which need to change something in the app can do it right away without breaking stuff. Try to do this on some custom app someone wrote long ago and has since left the company, and it will likely end with - I think we need to rewrite this thing...