Same reason people buy cars vs lease. It’s often cheaper if you’re buying transportation vs a new car.
If you know what you want, you’re better off running in your own AWS tenant or on-prem and avoiding whatever nickel and dime metrics a SaaS will throw your way.
They remind me of the "Clippy" era where people had little useless bots on their desktop like [1] Bonzi Buddy...
[1] https://en.wikipedia.org/wiki/BonziBuddy