@TDSgaming who ever said they didn't? it takes normal people YEARS to learn a language through proper instruction, and clearly there is no Japanese == Doggo Man Tongue guide. and that's assuming past humans even lived long enough to start to learn, after all the series already pointed out that a lot or possibly even most folks don't get humans as pets, they get them as dinner. AND that's further assuming what the author portrays as conversational bubbles between animal people is even a form of communication humans could mimic in the first place (admittedly it's fairly likely it is possible in general, but to what degree?) furthermore, I'm sure dialects (assuming that word would still apply as we're talking racial differences instead of regional ones) vary a great deal more than human ones do, I mean, a bird-girl with a beak wont be able to change sounds the same way a dog person would. and who knows what other races there are and how each of their dialects would differ? it might sound like each race is speaking an entirely different language to unknowing human ears, that'd make it even harder to learn.
you really ought to just accept the cuteness instead of questioning the world rules...I enjoy series like this more when I do...