I don’t understand why you think that second group is exclusively rich people. “These people are partying in weird outfits, therefore they must be rich”? Have you heard of, say, Mardi Gras?
I used to work at a gas station where one of my coworkers went to Hawaii for a week every two years. He’d save up his $7.50/hour, and get people to cover his shifts in advance, and everything was cool. Same applied to an awful lot of broke college students I knew–they might live on ramen the rest of the year, but by God they’d put enough aside to hit Myrtle Beach every spring break.
Step it up to middle class, and it’s even easier; most any low-end office worker can accumulate a week of leave in a year, and $1000 or so to spend on it, without special effort.
So where are you getting this notion that the concept of vacation is alien to all but the filthy rich?