It's much easier to put up indoor Christmas decorations where the family members can enjoy them. Fewer outdoor light does not mean Christmas isn't being celebrated any less, it's just celebrated more personally rather than publicly.
Fewer outdoor Christmas lights has been a general trend for the last 10-12 years. Outdoor lights are expensive to buy, difficult to hang, more difficult and sometimes dangerous to take down in snow and ice and the light strings are less reliable than they used to be. A few years ago light strings would only last about 3 seasons outdoors.
Towns are also scaling back on their downtown lights. They decorate the street light poles but no longer string lights across the streets (too much damage to the light poles from ice and high wind).