mint

i imagine it would cause all manner of headaches when you have conflicts between hostnames on a local domain and globally resolvable domains. don't know if that's why but it's definitely a problem with doing that

it primarily stems from logistical and also old networking structures. in the early days when the Internet was a garden wall, TLDs started being used to differentiate the usage of different sites (e.g. .mil, .gov, .edu) with .com joining the gang as a generic "contractor" type domain iirc. this also helps because on certain intranets, you can still access things without a FQDN, though this is much rarer these days unless you specifically set it up that way. for example, you may notice if you've done any personal server side projects, you're not using a FQDN, just http://localhost and a port number. now imagine if we didn't have TLDs - who would own localhost? who would own any arbitrary name? granted, the IETF has barred localhost from being used as a domain name anyway, but especially with the globalization of the internet, TLDs provide a ton of flexibility to be able to have your name still be concise, relevant, and memorable.

havign a difference between site in countries and stuff is pretty helpful