Why does everybody think the violin is the hardest instrument to learn?

Seriously, I understand that they have the melody most of the time, but the cello and b fingerboards are ENORMOUS and you have to press really hard to get a good sound. Cellos play really high up on their fingerboard quite often and the cellos also have the melody a lot of the time. So I don't get why everybody thinks the violin is the hardest instrument to learn, why not just say the violin/viola/cello/b because they all have their technicalities. Any thoughts?