would you pay $5 for a big list of world's airport WiFi free allowance so you know how much free time you get?
Don't I already find out when I'm at that airport? Do people usually change their travel plans based on airport wifi?
No. I'l find out when I'm at the airport. I wouldn't even download it if it was free of charge.
Plus I've never hit the limit. Probably because there are usually alternatives (other wifi hotspots, SIM card, changing MAC address, etc).