I have never understood that. I don't want any dick in my mouth, even my own. It seems like everyone always talks about it like it is some awesome thing to do, and then they are confused when I ask them what other dicks they suck.
I know, you might ask, I jerk myself off but don't want to jerk anyone else off, so how is this different? It's because it's a dick in your mouth, that's how! Totally different than blowing a load and getting some on your hand that you wash off.
In my opinion, if you seriously want to suck your own dick, you're gay. Which is fine, if you're actually gay!