An associated question is that, once you get into said lounges being a premium fare passenger, the US must be the only country where you have to pay for drinks. How did that difference happen ?
The US market is much more willing to pay for individual services. Club, checked luggage, better seats in Y, early boarding, premium security. Basically everything is for sale. And, people will pay.
Not always. In the US First Class is almost entirely occupied by the Upgraders who have regular coach tickets. Elsewhere in the world first/business class, other than for overcoming overbooking, is only accessed by paying the relevant higher fare.