You have the option. I don't do it often, but sometimes for a kid who is very involved in the extracurricular I lead, I will make a note at schools that also have the extracurricular about how they might contribute in that area at college.
But generally, I am writing these letters in the summer before I have an idea where the kid is applying. I write one letter, that is as positive as I can honestly make it for that child. Writing different letters for each school is not, in my opinion, a reasonable thing to ask.