I hate being schooled on a Saturday. I hope there's no homework, Toasted-teacher.
---
Despite clean practices and safety of using it, I'm still personally icked by the thought of it. The plastic itself is bacteriostatic, but is still a medium for products of normal body processes to collect on, be it bacteria, ooze of all sorts, or other things. Normally, that stuff is flushed out since it's not obstructed, reabsorbed into the epithelium, or destroyed by your immune system in small quantities.
I see it kind of like a band-aid on your finger. You can wash it thoroughly and with soap, but eventually it'll still get soggy and pick up lots of lint that you'll have to put a new one on.
But it's just my opinion; I don't like risks and carrying extra baggage on me. If you like it, rock on.
---
I like how they also drew the anus and rectum in the tutorial pic. Just so there is no confusion for users to shove it up their buttholes,