To clarify, I believe that seat belt usage, along with many other things, should not be legislated. The Constitution does not prohibit the implementation of a seatbelt law, nor does it outline the implementation of one. It is not an area of Constitutional law, so it becomes our responsibility to accurately and intelligently interpret the spirit of law and governance, and to not set unnecessary or deleterious precedents as we do so.
Further, laws like those regarding seatbelts are seldom passed by referendum or a proper vote. Often, they are imposed upon us by bureaucrats. Unfortunately, none of these avenues consistently takes into account our liberty, putting the onus of vigilance on us.
I very much wish that people would find the value in leaving well enough alone. There are certain laws that we need, and many that we don't.