Adding more decision making variables to the shot, like slope of the lie, fade and draw, variable and shifting winds, etc. will create more opportunity for player error and result in more bad shots.
As Genorb and others have said, it will widen the gap between the best players and the mediocre players. The best might lose two or three strokes per round, but the mediocre players might lose half a dozen because they don't know how to play the right shot.
Why would anyone think that's a bad thing?
I'm not pissed off because Ernie Els hits the ball more consistently than me. He's supposed to, he's better than me. I suck and he's a pro.
Genorb, Bollox, Dansamcam, RUNWME, blah blah blah, these guys are more than 10 strokes better than me, but I can keep it close because the game physics are simplistic, and they will get hit with random deviations as often as I will.
If the game physics become more complicated than "the hole is 10' above me and there's a 15 mph headwind" then I'm going to start making serious mental errors.
If I have to factor in a ball below my feet on a downhill lie, and I've got to curve it around a tree, there's a very real possibility that I'm going to put a crooked number on the card.
That's life. I suck.
If they can pull off that same shot and land it 10' from the pin, good for them. They earned it and I didn't.
This isn't tee ball. We don't get participation awards. Everybody doesn't get to win here.
To the people who think making the game "harder" (read as: more realistic) will cause people to leave in droves, I think that's horse puckey (as my grandfather used to say - except he said it convincingly and with a look on his face that made you think horse puckey, even though you didn't know exactly what is was, was some seriously messed up stuff).
Go to any municipal golf course on the planet and look at the sheer volume of people hacking up the course. Being bad is the rule and being good is the exception - not the other way around - but that hasn't stopped golf from growing at an exponential rate for the last 50 years.
But even if that wasn't true, look at it this way: The more decision making processes required to pull off a good shot, the less deviation (or VEM, or whatever we're calling it) is necessary to keep the scores from getting too absurdly low.
Right now, deviation is used by WGT as a way to mimic the millions of subtle variables in a golf shot. Lift your head and screw up your shot, bend your elbow wrong, break your wrist too late or too early, put the tee behind the wrong ear, breathe out of the wrong eyeball, and your shot will go haywire.
As more factors are included in the WGT golf shot, the need for artificial and arbitrary crapola deviation becomes less necessary because people will screw it up all on their own.
This is good for the game, even if it widens the gap between the best and the rest.