it has been that way for at least 30 years when I started paying attention to the summer camps.
The reason why, is because in addition to teaching skills in full padded practice, they use the camp to evaluate potential recruits, and frankly that is much more effective in live full padded work, and offers coming out of summer camp performances have been a long standing tradition from BYU.
There have been a few years where there were a session or 2 of shorter non-pads back when nike testing was done in provo at the same time as the camp, but it has been several years since that has been the case.