You know, we had often wondered the same thing. A few ski resorts offer limited hookups in the parking lot, but that seemed to us like camping in, well, a parking lot.
Here is an alternative -- it depends on some special conditions. Find a boondocking site not too far from the mountain. Wait till the snow level is just above the altitude of the campsite but not so late that the snow melts in the mountains. When all of those variables align, head on out!
That is what we did during the first week of March -- after a few days of skiing and snow-shoeing and snow-hiking, we got back home just before the Big Quarantine hit California. In this shot, I'm on the far left, and that is Parker Peak dominating the skyline. This site is north of June Mountain Ski Area:

Click For Full-Size Image.
And here is the blog post, with more photos. (I was going to say "feel free to check it out if you have a few minutes," but most of us have lots of time on our hands these days.)
Skiing While Boondocking