Maybe in your campaign world, but no one gets new spells for free when I DM. Some spells do not even exist unless a PC wants to spend time and resources and try and research it and be the creator of the spell. That way it can be named after them and not some no-name from another dimension. lolBy the time a wizard is 20th level, he's been able to add six 9th level spells to his spellbook just from leveling up. So he doesn't need to find wish at all- at least by RAW.