People pull guard frequently in the Mundials as well as Abu Dhabi. Those competitors might not all be olympic caliber judoka or wrestlers, but I'm sure they have some pretty damn good standing skills for the most part.
I'm not sure about Mundials, but in ADCC pulling guard is becoming less frequent all the time, as competitors' standup skills have been improving. And in MMA pulling guard has become downright rare, because people learned to defend against it.
No matter how good you are standing, it's impossible to stop a guard pull. Jumping guard, yes this is very possible to stop. But if someone wants to pull guard on you, he WILL. It's not difficult to grab a sleeve, foot on the hip and simply lay back.
Actually it's pretty easy to stop a guard pull, you just strip the grip. Foot on hip and lay back isn't close to being enough to pull a trained grapper down, most competitive guys can stand up all day under those circumstances, and they only need a second to strip the grip (often not even that long - the really good guys strip the grip as soon as you get it). In fact, if you go to the judo forums you'll read a lot of old time judoka complaining about how much competition judo has turned into grip fighting experts who strip grips so fast no one can throw.
Compounding this, if the guard pull is the only move you have (ie you have no other takedowns or throws) its trivial to stop. Mind you, if you only have one throw or takedown, it doesn't matter what it is, its easy to stop. Good takedowns usually come because your opponent has to worry about a number of possibilities. Its like sweeps on the ground - if I can only do one sweep, how long is it going to take you to figure out how to avoid or counter it? The same thing happens with takedowns, people adapt, especially between tournaments.
The exception is under some rules where stripping the grip and backing out is considered avoiding contact and is penalized (ie you're supposed to follow to the ground). If you're fighting under those rules then yes, its hard to stop a guard pull, simply because as soon as your opponent sits down with a hand on you you're obliged to follow, even if you can easily back off and strip the grip.
BTW, against someone with good grip fighting its almost impossible to get a grip strong enough to do anything unless you're very good at it yourself - if you've ever worked with a guy like the Canadian national judo coach (and double olympic medalist) Nick Gill you'll know what I mean. Even olympic level matches often go almost the full five minutes without either guy getting any sort of grip - makes for boring matches and referees will penalize it for defensive fighting sometimes, but it shows you how hard it can be to get a strong enough grip to do anything (like pull someone down). We've got a few guys in the club I never get a decent grip on, though I think my technique is better in other ways (and I think they'd lose by defensive fighting penalties if we fought in competition ... at least that's what I tell them :icon_chee).