Ofcourse, everyone has their own preference. Thats an interesting perspective as well. My only counter to that would be that its time consuming to roll your own auth for a complex or large scale app. It starts off easy but soon you have to make significant investments in various aspects of auth. That isnt true for all apps ofcourse. Definitely good to keep learning though!
Part of it too is that I tend to work on smaller projects that don’t grow and change indefinitely like startup saas does. If you’re getting something up quickly where the requirements will change all the time, a service like this starts to make way more sense :)