As a structural engineer most of my work day involves technical models or calculations, and I'm expected to be far too serious and "professional", so its great to be able to unwind and be rather stupid or creative and free to do whatever I want want in my YouTube videos (however crappy/embarrassing some end up being - esp with hindsight!). I also love creating a new animated title or special/visual effect or trying out an editing technique.
Finally I'm still amazed by just how powerful tools we have and how cheap/accessible technology has made these. As a young kid, I would try and create animated scenes by cutting and taping A4 sheets into a really long roll and drawing out a scene frame by frame, and wrapping it round two old loo rolls which fitted round spindles at either end of an old shoe box which had a cut out viewing window. Quickly spinning one loo roll would produce a vague film!! Then 10 years ago I got my first digital camera and raided every lamp I could find in my house and anything I could use as a prop/make-up/be useful and was really excited to be able to burn my own short film onto a VCD. Today if I were really dedicated (over many years to learn!) the technology is there to create something that would have cost 1000's if not 10'000's when I was that kid with the loo rolls, scissors, tape and pencils! What's more Youtube allows anyone in the world to interact immediately and for me to bounce ideas with anyone anywhere! I feel YouTube is just one part which gets me so excited and motivated to continue my hobby - and who knows what the future holds