Who keeps their boots in a bag? Some bags are compact and the boots just clip onto the outside. It's convenient.
I bet that smells nice. Do they actually have good places to sit in your lodge where people won't just run into you and try to kick your head when you bend over? There called lockers
I see people doing it everywhere I ski. Sometimes it seems like some sort of contest to see who can have the most stuff.
Having extra gloves, lens, lunch, tool, tape etc is smart.
If it's a contest the racers are winning for sure. They have so much stuff on hill, boot bags, multiple pairs of skis, race gates, tools, pretty much everything but the party. Super important part of the day is when they parade down the hill with their gear. To be a cool girl you need to do the ski parade with a giant boot bag and an extra pair of skis on your shoulder.