To answer the question about the frequent flyer miles: Many credit cards have rewards programs where for every dollar you spend, you get 1 or 2 points in an airline miles points programs. For example, my card is linked to my Delta account so I charge everything -- utilities, groceries, gas, everything -- to maximize my miles. It works out to about one free plane ticket a year.
Maybe Ross was trying to claim he started using the credit card a lot to accrue more miles. But 4,000 miles won't really get you anywhere. It was just a way to try to make himself sound financially savvy and shrewd rather than a doofus in more debt than he could handle. $4,000 is a lot of debt on a $60K/year income.