Here are two common arguments in favor of keeping things the same.
Teens these days may not be as physically active as they ought to be, but they're definitely busy. School, extracurricular activities, jobs, and social events usually require some form of transportation.
If the teens can’t drive themselves, the responsibility for transportation often falls to their parents—who may not have the time or ability—or to public transportation, which may not be readily available. And with most American cities being built with drivers in mind, walking or biking long distances may not be practical or safe either.
All in all, fewer transportation options could limit the opportunities kids have for personal growth at a critical age.
The argument here is that the higher crash rates for 16- and 17-year-olds may just be because they are new to driving and lack experience. Delaying the start of driving may just delay that learning and shift the crash rates more toward the 18- and 19-year-olds.