We use this for summer camp. The kids aren't allowed anywhere near computers or phones, let alone internet access. So we write them emails and attach photos that are printed out and delivered to their bunks.
I attended summer camps as a kid and worked at one for years as an older teenager. I love summer camps. Looking back, part of the magic for me was being away from my parents for an extended time in a way that wasn't really possible in any other setting. The service you linked (a way for parents to constantly follow along with what's going on at camp) just feels... wrong? unnecessary? detrimental? to me. Do parents really need to be updated all the time with what's going on while their children are away for a week or two?
I don't think it's immoral or unethical to offer this service, I'm sure there's a market for it, but I just don't see why anyone would choose to use it. Let the kids go off to camp and have a good time, and they can tell you about it when they get home. It would really take the wind out of my sails if I got home and my parents already knew everything I had done, instead of getting to tell them all about it myself.
The campers are definitely encouraged, and sometimes required, to write letters by hand. In fact their handwriting is much often better than adults, because they write by hand much more frequently.
The service is https://www.bunk1.com/