To add to that, imagine getting asked the same esoteric questions all day long dozens of times, over and over again. Then if you're there for multiple days you're getting asked same old questions multiple times all day for however many days you're there for. Then when you're done, you go to another con where all of this happens all over again. With that in mind, it's a wonder any celebrity is decent at a signing/con.
I don't know, I've always thought Mark Hamill would love me asking "Did you think Star Wars would be a success while filming?" :lol I'm still waiting for him to snap and jump over the table at someone who asks that.