Doping is not acceptable in sporting activities, and all professional and none professional athletes are aware of this. I feel, the main reason why some of these athletes indulge in this doping stuff is probably because they are desperate to earning their spot. I
Yes, that's right, wherever it is, in all sports, doping is not acceptable. There are several histories of athletes or sports players who had to pay fines and also return the medals they had won during that time, because they were proven to have used doping. Yes, this is unprofessional, and violates the main principles of athletes, and cheats other players or athletes too, it's unfair. That's why the sanctions are usually that severe.
For Pogba, this is also one of the reasons Juventus did not accept him back in the team, besides because they already have other players in his position, and several other things that made Juventus consider that Pogba was no longer fit to compete in Serie A, even in Europe.