You have to resort to setting up an ftp server and/or download extra apps on your phone for this, whereas Bluetooth file sharing is standardized and should work out of the box on any phone brand or OS (not sure on iPhones though) and anyone should know how to use it without needing any third party apps.
Material Files is an Android file manager that adds the missing ftp support.
Start/stop the ftp server with a single click. I have yet to find anything easier.
Plus, non-iOS/Android feature phones don't have ftp support but they do have bluetooth so this cross-compatibility out of the box is another advantage.
That's why Apple is a multi-trillion dollar company. Because people want the easy way. If things require extra apps, extra steps and reading tutorials/instructions to use, you can bet most people will stop right there.
I'm not disagreeing with you, I'm just saying how things work for the masses.
I call it the (grand)parents test. If they can't figure it out on their own then it's not user friendly enough.