What's up with blind tags?

[AareDub]

Like when the ref is over yelling at one team, the legal man for the other team gets on the apron, makes a clap sound, and the other guy goes in as the new legal guy. They faked a tag to get cheap heat I guess.

WTF is the point? He's standing right there, he could just tag him. It's not like he's getting away with some crazy illegal jedi mind trick shit or anything. I guess it isn't seen too much in the WWE anymore, but I see it a lot at indy shows.