Hey, I'll be your friend too if you bring me $500 pure profit every couple of years!
For me, Zenni is even more convenient than Lenscrafters. Lenscrafters doesn't carry my prescription in stock, so they have to send out for the lenses and I have to return to the store one or two weeks later to pick up the glasses. With Zenni they deliver right to my mailbox in about the same amount of time.
Back in the good old days glasses were actually carefully fitted to one's head and it made sense to go to a well-skilled optician. These days they're spring-loaded and the Lenscrafters people just slap them on you and say "Is that OK?" I can do that for myself!