“lilmod ulelamaid – why cant it be? its just as bad.”
We don’t decide how bad something is based on our feelings. No Gadol says it’s just as bad as not being shomer negiah. Being shomer negiah may be “yeihareig v’al yaavor”. Any Gadol will tell you that if you have to choose between smoking and not being shomer negiah, it is a million times better to smoke.
It is possible that some of these bochurim are smoking rather than being “over” on serious aveiros that one is chayiv misa or kares for.