Though this might be due to cops wanting to keep their own local ‘war on drugs’ going on. The statistics won't improve themselves, you know. And I know for certain that cops are aware of Tor and what people do on it.
Edit: wow, fastest downvotes in the West are coming immediately after posting in this thread. Like, less than ten seconds passed.
Upd: somebody posted a reply but deleted it before I started typing my own (what's even happening here?), so here goes. What I'm saying is that I can only wonder why Russia doesn't block Tor and would very much like to know the reason. However, I do think that the FSB might be interested in hijacking Tor traffic, even if just for shits and giggles at first. And buying some boxes in Hetzner probably isn't a problem for them. Don't forget also that FSB directly works with several criminal hacker groups here, and having both their own masqueraded Tor routes and hijacking others' traffic might be vaguely titillating for those people.
As for blocking Tor, I already mentioned that the site would be easily blocked with existing measures, as would relay IPs. For more covert nodes, afaik DPI is being implemented across the providers currently, on RosKomNadzor's orders. So I guess we might yet see Tor blocked on the protocol level (possibly along with Telegram?).