That was tried but they have many millions of smokers so have held on and the political types do not want to piss off that many voters. Instead they are just doing it a little at a time. Vaping does not have that many people using their products so would not be able to withstand lawsuit judgements in the hundreds of million dollar range like tobacco companies.
Philip Morris and RJ Reynolds have billions tied up in vapor. They missed the initial curve, they thought it'd go the way radio thought the TV would go... flash in the pan. Although their clientell is continually dying and quitting, they still rake in mass amount of money. Like you said, they're also heavily invested in politicians. They're not going anywhere, nor is vaping. They've spent too much to lose the same demo that quit once before.