Is it rude to sit on druids?

As stupid as it sounds, this is an actual question.See, i am a DK, which means I am not particularly fast. In mythic+ especially I can be lagging behind in some areas, despite Wraithwalk (lol). So if we have a druid in the group and they use their horsey-form to run, i just tend to hop on them, since they instantly transform and it saves me the time to summon my mount.Many transform back and straight into travelform tho when i do that. I mean, i am a big, fat orc in propably really heavy armor and i don't smell nice, but it speeds things up, so why do i get thrown off? Am i missing some mechanic?Sorry to all druids for not knowing your culture. I have many many druid-friends tho and trees are super rad, right? Yay Malfurion and stuff.