Yosemite has lots rescues because it has lots of use. Some relatively dangerous places are easily accessible (seasonally very swift water even next to roads). Many trails are quite strenuous, iniviting those who probably should not go up them. Yosemite is also a world class climbing center - very difficult climbs- requiring a specialized rescue team for climbing rescues. I do not think a book of rescue details in a gift shop would make a lick of difference. There are plenty of signs of the dangers, and many people just ignore them anyway. I think a bit of the problem is the glorification of stupidity that is shown on reality TV that young people now are watching.