Why are these apps on bluetooth? I'm surprised no one has come up with a way to transmit data over local ad hoc wifi networks, it must surely be more simple if you could make some sort of transient hot spot

Bluetooth works most reliably across all devices (within its limited range), but all these p2p apps are indeed moving towards multi-transport support to diversify and widen the connectivity grid: https://hackmd.io/@grjte/bitchat-wifi-aware