One of the things Teller (the magician) talks about is that while obviously you do want the audience to be "fooled" in some sense - that's what they're paying you for - you don't want to do that by straight lying to them. Where's the fun in that?

The goal is to create a scenario in which the audience knows they were tricked but can't figure out how. So you don't lie and say this is a random audience member when it's actually an employee "stooge". But when you're giving the genuinely random audience member a "free choice" of cards you don't need to explicitly tell the audience that, duh, as a magician you're not giving anybody a truly "free choice" of anything actually and you knew immediately which card they picked even without seeing it. That sort of thing.