The governments role in regulating anything is set by the constitution. It’s not based on “times change” “the constitution is a living breathing document” “save people from themselves” arguments. That is the entire concept of liberalism.
Conservatives believe in the constitution, limited government power (limited by the constitution), and freedom. Even if it’s freedom to be an idiot.
“E-cigarettes” (which is a clear misnomer) are significantly safer than smoking. They don’t stink, they aren’t filthy, and they don’t cause cancer. You can not like vaping, that is your perogative, but the risk reduction over smoking is significant.
“E-cigarettes” also save lives.
And, cut deeply into government tax revenue.
Which is what really scares the big government types.