They aren't road legal by EU laws either, although there are a hand full of owners from EU countries (Poland, Czech Republic, Austria) that managed to get theirs registered through exceptions.
I think it's the (fear of) drones. Most russian troops don't have any effective detection or countermeasures against them. Artillery hits are often followed up by drone attacks and Ukrainian infantry also heavily relies on reconnaissance and support from drones.
There are so many videos from the early stages of the war starting with a single russian soldier getting wounded by artillery, a drone grenade, mine or sniper. Attempts to rescue them then lead to more and more drone casualties. Getting stuck in this situation then makes it a matter of time before artillery, more drones, or Ukrainian ground troops show up to finish the job.
The result are panicked retreats where everyone tries to save themselves. The general lack of training and resources probably doesn't help either.
I'm always baffled how pointless that subreddit is. Almost every question asked there barely requires any math. Usually it's just look up two numbers and then do one basic operation. Or even worse, questions that aren't even answered by math at all.
The title of the study is "In a narcotic trance, or stimulants in Germanic communities of the Roman period"
Its literally the first result if you Google "Praehistorische Zeitschrift Stimulants". It's pretty easy to find.