The top players (apple/samsung) have switched to proprietary stacks on top of bluetooth to get the "magic" pairing experience. Google is following suite soon. On non "magic" pairing devices, bt is still a pain in the ass to get to work comparatively.

Imagine if you had to do the standard bt pairing process for wifi. Device to connect to has to be broadcasting, Device trying to connect has to be listening, after connection you have to ensure that the passcodes are the same etc etc. If the connection drops then repeat the process sometimes(<BT 5.0).