Excuses, excuses.
I know a fair number of folks that have quit smoking both pot and cigarettes. Not one of them has ever said they regretted the choice.
I know even more people that have tried to quit, but failed. They generally admit that they would still quit if they could.
I don't know anybody that started smoking anything late in life that declared "Gee ! I sure wish I had started sooner!"
I have seen LOTS of young men ruin their lives by spending that weekly check on another stash of weed while the kids go hungry, the wife wishes for better things, and my employee just wastes it all on brain dilution. It doesn't matter if it is weed, cigarettes, booze, or any of the harder stuff. It all ruins your health, distorts your perception of reality, and wastes your money.
Justifying one bad habit by comparing it to another one is foolish.
An economic note: if you burn a pack of cigarettes per day (@ $3.00/pack), starting at 18 years old, by the time you are 65, you will have burned up your retirement. If invested at 10%, calculated on a avg daily balance, that will come to $1,196,489.03. Add a quart of beer at $2.00 per day, and a trip to a fast food at $5.00 per day, that comes to $3,988,296.78 you blew during your working years.
Put that in your pipe and smoke it!