As a 22 year old that just got back, I was carded nearly everywhere I went, including when I checked in at Excalibur and New York New York (I didn't like the possibility of staying at a Delta-provided airport hotel last night, so I booked a cheap room at NYNY instead to stay on strip). Check-in, bars, etc. there was someone asking for my ID. Only place I didn't get ID'd was when I was gambling.