Don't make sense

So how and why can you do challenges and get rewards weekly tokens and such then spend them for sets but can't do nothing but play with the player or sell the player for training 🤔 you should be able to sell for coins as well to upgrade players and get new players . Then how can you buy packs from the store and the same issue happens where im spending coins and can only sell the player for training 🤔 its gotta be glitches just has to be