That's because of the incredibly short range. I thought very seriously about trying to set it up on my computer so that I could leave it running at all times as a relay. But that turned out to be a total pain in the ass, so I gave up on the idea. My thought was my computer hosts my Monero node and so is on all the time anyway. I might as well run a bitchat relay on it in order to improve the network. But compiling software was my downfall.