YABU. Though I do understand your point about developing a work ethic and getting a taste of how shitty a low paid job can be.
You are more than a little U to think that anyone would employ them full time for just 8 weeks.
My DCs all had summer work but we are in a place where they get just under three months off, so it's worth an employer's while to take the time to train them. There is also a good deal of seasonal work here (public pools, parks and rec, summer camps needing teens, and a culture where parents are happy to leave school age children in the care of virtually unknown teens during the summer recess).
Actually, come to think of it, my DCs all worked doing babysitting and weekend DIY help all year, not just in the summers. That is how they had the references that got them the summer jobs. We also had a contact who was happy to employ the oldest three in turn in an office doing filing and the coffee run and part time receptionist duty, plus the local parish employed teens for half the day on Saturday or Sunday, answering phones, photocopying, dealing with people complaining about the sermons, redirecting homeless people to the services available - lots of good experience.
I disagree with people who say it's fine to not work based on the idea that youth is a precious time. Teens gain immensely in the self esteem department from earning money, from learning a job, from having their own money to spend on whatever they want, and to give them a feeling of independence.
And without a few items on your CV it's hard to get a job once 'the rest of your life' starts. My DDs1 and 2 had several items on their CVs by the time they left high school and by their last year of university they both had a few more. They were hired on their career track jobs before they graduated.