The lack of a cable saves a bunch of space and avoids the floppy cable. Probably irrelevant if you don’t game, but definitely quite convenient for FPSes.
I have to agree, specifically mice have been the least painful Bluetooth experience for me, with a Microsoft. Annoying part is that it changes MAC address when pairing, so regularly using it for more than one computer is a frustration but that's nothing compared to the constant interruptions I've had with keyboards and codec issues with headsets.
Like you, I have a "gaming" mouse (G700s), in my case I bought it for the high resolution. I used to have g9x, but it developed an unbearable whine. Battery life is downright atrocious, I basically have to recharge it everyday. It's also comically heavy.
I often have to move things around my desk, and having papers getting caught up in the wires is aggravating. Also, apart from gaming mice with very supple cables, I always found wired mice to be a pain because of the wire that's never quite in the right position and pulling and / or getting caught on things.
The same happens with keyboards, but to a lesser degree. I often use a trackball, which is like a keyboard in that it doesn't move around and I still prefer having those wireless.
I will never use a bluetooth headset, the technology is not there yet. Latency and battery usage of bluetooth audio devices are inconvenient and I don't understand people can bear with it.