Now that Pokemon is released globally on the same day, or at least close releases for each region, why does Japan still get 10x the events everyone else gets? It also seems like NA gets the least! I go to the Serebii website to check the events for X/Y and ORAS, and Japan has a ton of events for regular Pokemon and legendaries. North America seems to get the launch event and then something like Gengar. So unfair, especially when we have the internet that is able to handle all events.
Because event distributions have got nothing to do with whether or not the game came out on the same day. They are unconnected.
Japan gets more event distributions because they have more places willing to hold it. Pokémon Centers with events, special promotional places like the Pokémon Lab and Pikachu Outbreakchu with their distributions and so forth. America/Europe doesn't have that because it seems places are less willing to hold events and Pokémon isn't as large as it is over there.
They want their events to have context. They very rarely give Pokémon out for the sake of giving them out, but rather to tie in with something. The distribution is seldom the main thing, it's a bonus for going to something else and the Pokémon given is tied in with that i.e. Teeter Dance Pikachu because of the dance focused Pikachu Outbreakchu, Shiny Gyarados because Red Gyarados is the mascot of the new Pokémon Center, Jirachi because of the Tanabata Festival etc. and these meanings would be lost and they don't want that. Event distributions for the sake of event distributions is not part of their vision. Besides, we get the vast majority of all important ones.
Plus, what people often seem to miss is that it isn't just "Japan getting the events", it's quite often that it's just one building in all of Japan hosting it. That locks many out of getting it. It's not cheap to travel across Japan
When did this new designation of Mythical Pokemon become a thing? What the difference between Legendaries and Mythicals?
Happened quite a while ago. Mythicals are essentially the official name for Event-Only Pokémon so Mew, Celebi, Jirachi, Deoxys (even though it's wild in ORAS), Manaphy, Darkrai, Shaymin, Arceus, Victini, Keldeo, Meloetta, Genesect, Diancie & Hoopa