Au contraire. Many ski towns have bustling summer activity and Jackson is one of them. It's full of tourists winter and summer. It hosts a spectacular music festival called The Grand Teton Music Festival and people and musicians come from all over to listen. The town is close to two jaw-dropping National Parks that are inundated with visitors all summer long, though I doubt H&M came for the scenery.It's a high end ski destination - a more adventurous Aspen. But no reason to be there in summer - God knows Meghan wouldn't be seen dead in most places off season. So maybe it wasn't them.
The dull seasons are spring and fall, affectionately called mud season in ski towns. The surrounding area is extremely wealthy and populated with low-key old money people. Ever watch Yellowstone?
Most visitors come to spend their time fishing, horseback riding, and hiking through the area's beautiful mountains. I'm sure the Markle's are after financial backers.