At the end of the day MLP is a cartoon aimed at kids in the U.S. (or, more broadly, at Western countries) and as such has to be relatable to them, including in slang and the like.
I do think, however, it's done an admirable job of conveying a recognizable society, yet one where sentient ponies, magic, and fantastic creatures exist. Or example, holidays and life milestones that seem plausible within their world, but we could imagine ourselves celebrating something similar.