I got this question a few times early in magic start and realized if they are asking then I must be showing them something pretty damn boring. They should be amazed with what you can do, which is what you presented. See the point.
No jokes come to mind Steerpike, except maybe
"Can you Levitate?" Spec
"Well, can you?" Me
"No" Spec
"Guess we're on a even playing ground then." Me
Geez that's a horrible joke, oh well instead of trying to come up with witty comebacks and failing like I just showed a first class example of. Try to work on why they would be bored, maybe because they don't give a s**t about two cards being sandwhiched.
It's all about the performance kiddies, you show them something they want to see and they won't worry about what they aren't seeing.