Although...different use-cases there, for me. I've got a dozen audio sources, either connected to speakers (the TVs) or within a couple feet of me when I'm using it (phone, media player, tablet, laptop). So, a bunch of sources, a couple of which I might be listening to at once. All either in short enough distance for cords, or loud enough that it's moot.
Wifi: The internet comes from one (inconvenient) place in the home that I can't choose. I've got a couple of powerline ethernet adapters, but I've also got a lot of devices that handle wifi, but not ethernet. The choice is between using wifi or skipping the network connection. It's great as a last- (or only)-resort connection option, and it's usually sufficient, but then my uses for it are usually pretty tame anyhow.
Wifi has encryption. Bluetooth means I'm broadcasting my audio stream to anybody who feels like snooping on me.
Not quite.
Bluetooth was originally encrypted, but gained the option of non-encrypted channels with version 1.1.
On top of that Bluetooth use frequency hopping.
Until recently there was no real hardware for scanning/sniffing Bluetooth traffic, at least not anything easily available compared to a wifi card in promiscuous mode.
As a matter of fact, my desktop & my laptop are both wired, and I hate how flaky WiFi is on my phone & tablet. Just moving to different rooms in my (small house) does horrible things to my network connexion speed — but Ethernet keeps on chugging along.
The same as wifi, right? Strictly worse in every way. Except for the not needing wires way.