A trend I love!
Every year my AP science class is full of kids who are taking 3-5 AP classes. Last year, I had a child who would break down in tears about three times a month because she had a schedule full of AP classes, played school soccer, travel soccer, was student council blah blah, FFA officer, in pageant, and it just went on and on.
This year about a third of my kids opted out of taking the AP exams because according to them, colleges don't even look at weighted GPA. So they use the class as an orientation to college level classes rather than to replace credits.
I personally think the over committed kid actually is less prepared for college than the focused kid. I'll certainly be guiding my little one into top classes (honors) but not demanding AP. Especially if she continues training this sport at her current level or higher.
They don't look at the weighted GPA because all the schools weight them differently. They do look at class rank though, which is affected by weight.
How much that matters depends on the college you're trying to get into.
Also personally I would have hated to do enough work to get a good grade and the go to college with no credit to show for it, so that's a factor to consider.
It IS very important to colleges that students show that they took advantage of a rigorous course schedule offered at their high school. I suppose that isn't really affected by whether or not they actually take the exam. In the school system I went to high school in, you're required to take the corresponding AP/IB exam, though.