They start early because it's how you get the mountain open, one run at a time, until there is a natural snow base. You don't lap a run for several hours to get your legs under you in April, but you do in Oct and Nov.
Most people start their seasons lapping groomed terrain. A WROD is just a groomed run, nothing more or less. This was from Loveland's opening day. What about that is there not to get?
Well, I could be mistaken, but I've always thought of a WROD as, literally, a ribbon, with brown on both sides. Generally it's made of artificial snow because there hasn't been adequate natural snow, and often that artificial snow was made under marginal conditions so that it's dense, wet and icy. Everybody at the area is forced onto this ribbon because that's all there is. So you have the racers in early season training competing with anxious unguided missiles with poor steering and speed control skills, and everybody in between. Hence the D of WROD.
That's less than a regular groomed run, in my book.
What you have above is a nice, possibly exceptional, opening day at a high altitude area. There is no ribbon, since coverage extends past the reach of the snow guns. Where I ski now, there is no snowmaking and no WROD in the early season. The place usually has over 4 feet of snow on the ground when they open - in December. They have some grooming, but no ribbons.
If opening day everywhere looked like it did at Loveland in your picture, I'd say, "Great. Let the games begin!" But it doesn't, and several photos earlier in the thread illustrate the traditional WROD quite nicely. No, thank you.