I want get my achievements eventhough playing offline on Minecraft PE

Minecraft, one of my favorite games, I love and recommend. I don't regret finally buying it. But, well... One of the advantages of having the game paid would be to play with achievements but I don't know why I can't play like this offline. I enter the game and not even my skins are there and I don't have the possibility to always be connected and that kills my experience 😕. Why can't I have these things offline? I know, you probably have a reason to it this way but why do not do it like YouTube does asking for verification after 1 month to keep the content?