That's only true because it has been engineered to only be that way.
For example many pieces of software that used to be syncable through bring your own options have dropped those in favor of charging for their sync capabilities.
I am incredibly tired of it. I cancelled every subscription except what I need for my job, and I'm working on moving to one time payment and free software there too.
I've discovered the joy of hosting my own services at my own home, and it has been life changing.
For example many pieces of software that used to be syncable through bring your own options have dropped those in favor of charging for their sync capabilities.