If there are only three artists I want to see, I most certainly am not paying upwards of 80$ a day, plus transportation/lodging, to see those artists play for half the time they would if I saw them at a proper venue only for it potentially to get canceled due to rain because its outdoors.
The rain part is very understandable, but Lolla is rain or shine. It actually made for some pretty gnarly sets last year on Sunday. We had a downpour around 4:00 PM or so and then later around 8:00 PM right before or during the final acts. Look up footage on YouTube of Cage the Elephant, Foo Fighters, Cold War Kids, or Deadmau5 from last year and you can see what I mean.
And most of the acts get a forty-five minute to an hour slot too so it makes for a pretty satisfying set time. The past two years I've seen my favorite bands play everything I'd want to hear from them.