I don't understand the logic on how a lobbied multiplayer would somehow all of the sudden start getting every designer plays. It wouldn't change anything in that respect. People would still play the same courses they are playing now and still discover new courses just the same as they are currently doing.
A Multiplayer lobby to me, isn't about getting a designers courses more plays, it's simplifying anyone who owns the game, a streamlined option to find a match to play with live folk nearly anytime we turn the game on, friends or not. There's no fear for me playing a complete stranger, even the online friends we have now were strangers once, unless you know them ALL personally. It's not even close to real life, it's a video game, with people enjoying a virtual game of golf over a network. If you don't want to play with someone, then don't.
On the contrary to your above statement, I'm sure the opposite would apply. I bet I would play more courses I've never knew existed, by being able to join a match with anyone, anytime, in a true multiplayer setup.
Multiplayer lobbies were practically invented, because of golf games. It's a MUST for these low tempo, kick back, playful banter, type of games, such as online billiards, or a Texas Hold'em game. I still shake my head at how this was not even put in, from the get go, or even shortly after the games release.