When did this start?

I always thought the practice of a pitcher or other player putting his glove over his face when he talked a bit odd.

It looks extra strange when there are two or three players talking to each other on the mound, and they all have their gloves over their faces.

I know why they do it. They're afraid someone on an opposing team is watching a telecast of the game and trying to read their lips. But my question is, what kind of scarred-for-life moment caused almost every player to do this whenever there is a conference on the mound? Because don't you think someone had to be really successful in reading lips for this "talking into my glove" practice to become epidemic in baseball?

If there was a famous moment when some team capitalized on information gleaned from reading lips, I'd love to know about it.

I'm trying to remember how long this has been going on. Ten years maybe? It certainly wasn't happening when I was watching games growing up. Maybe it's just general paranoia since every game is televised nationwide now and every shot can be zoomed in on and slowed down to frame-by-frame action.

Or maybe it doesn't have anything to do with the game at all. Maybe players just don't want viewers to know they're talking about the hot blonde in the third row.

Or, maybe it's this (commence random, fake conversation):

Red Sox catcher (either Varitek or Kottaras or Cash, I don't know which): Hey, did you hear Nachos Grande pulled a Clayton Kershaw auto and a Russell Martin silk card out of his box of Allen & Ginter?
Beckett: No way.
V or K or C: Yes way. That was Night Owl's box don't you think?
Beckett: Yeah, I think so. Must've got 'em mixed up.
V or K or C: Don't you think he should send those cards to Night Owl since he obviously got the wrong box?
Beckett: You bet.
V or K or C: It's just common courtesy. The honorable thing to do.
Beckett: No question. ... Um, so you think I should knock this guy down?
V or K or C: Never mind that. Nine o'clock, hot blonde in the third row.
Beckett: Decoy. My wife's in the stands. She wants to see if I look.
V or K or C: Well, if you cover your entire face with your glove, instead of just your mouth, and look through the webbing, nobody will know.
Beckett: Great idea! You're the best. I'll give it a try ... So, I'd do it like this? ... Hey ... Hey! I can't breathe! I can't breathe!
V or K or C: Pull the glove away from your face! Away from your face!
Beckett: Oh ... ah, that's better. ... Damn, she is hot.
V or K or C: Told you.
Beckett: You always come through. So, uh, which catcher are you again?