Your example of drugs is an activity which is specifically banned in cycling
Banned, yes... But it still happens. Mainly at the behest the teams, rather than individuals.
Where you have professional sport, you have unscrupulous people, whether they are some of the parasites in boxing pushing washed-up fighters into one more payday, or the "doctors" in cycling giving young men concoctions which they tell them are "vitamins".
One sport has a brutality to it, which to some people is balletic, some people poetic, and yet others viscerally repugnant (and I can understand that last viewpoint, I feel the same about bullfighting). The other has many of the same virtues, yet whilst it lacks the raw brutality it possesses an insidious deviousness, much more than one finds in prizefighting.
Either way, young lads can get their health ruined by the unscrupulous.
I like boxing, as an athletic pursuit; but I'll be the first to admit that there's a lot wrong with the professional side of the sport. I love cycling, otherwise I wouldn't be here; but, my goodness, there's a heck of a lot wrong with the professional side of that, too.
Put it another way; boxing's governing bodies have a history of trying to alleviate the dangers in their sport. Cycling's, for far too long, turned a blind eye to theirs.