That simply isn't true.

A lot of servers spend time doing during their shifts - if someone is scheduled on from 12pm-8pm. yes, they will be very busy from 12-2, and from, say 6-8 during the lunch and dinner rushes. But how many people are eating at a restaurant at 3pm on a Tuesday? Not very many at all, maybe the odd person dropping in for a drink. During those times, servers will sit around talking, especially if the boss isn't there, or take forever doing menial tasks like wrapping napkins etc. One restaurant I go to regularly, the servers take smoke breaks (since they know me, they pop by and check if I need anything before they go for their cigarette 'going for a smoke, back in 10' style). I often see them standing chatting to each other in the service area or hanging out on the patio chatting to customers. I frequently see servers messaging on / reading their phones.

Bartending / serving is a pretty easy gig - I did it for a few years while at university. Yes, there are days you are rushed off your feet, but it makes the time pass quickly. Other days it is slow as heck, say afternoons in January, where you have already cleaned everything, rotated all the stock, so even management are fine with you sitting and reading the paper (this was pre smart phones!)