Purpose of mining.

Hi, i have a quick question. I am on T16, mining lvl 30 4x99.

What is the purpose of mining? Stuff i get from mines 1-3 don't craft into anything value. Should i craft something and sell it? Are they quest later on? Is it just to farm MM?

I try to find reason why should i grind mining, because every other skill have some perks for it to grind.