“if a Windows XP machine had an ad-hoc network favorited (which would be default if it had ever connected to one), then when it wasn’t connected to any other WiFi network, it would beacon the favorited ad-hoc network to make it easier for other hosts to connect.”
“Free Public WiFi” never offered internet. It was an ad-hoc network someone made once before 2006, and Windows XP’s Wireless Zero remembered it and rebroadcast it from every laptop that ever joined. Hotels charged $15 a day for real WiFi, so desperate travelers kept connecting and kept spreading it. Microsoft shipped a worm and called it a convenience feature.