Prohibition did fail and US had to revert ban on alcohol.

The rules are made by politicians.

All it takes to change the rules is to rotate politicians.

Or enough public dissent that the same politicians are forced to revert the rules.

A smoking ban could easily be enforced by allowing anyone bothered by secondhand smoke to report it.

Is weed legal in the UK? Do people still smoke it?

This might play right into the hands of bootleggers and gangs but also into the Swedish / American nicotine pouch industry which is basically marketing straight at kids.

Also - vapes. Most folks don’t smoke cigarettes anymore. How does this control vaping?

There is a big difference between weed and tobacco.

I am a fairly regular weed smoker. I used to grow my own. I used to smoke tobacco. I can go weeks, months and even years without smoking weed. Kicking my nicotine habit took many, many, many tries and I didn't even enjoy it! They are not the same.

That's a different in the harm, not a difference in the effectiveness of prohibition. In fact, the more addictive the substance, the less effective I would expected prohibition to be (and the more ancillary harms to result, especially from criminalisation).

That's exactly what this is. The money has moved on to pouches and vapes.

It's like how everyone pat themselves on the back for banning child labor after the industrial revolution had rendered it obsolete outside a few niches that weren't economically important enough to put up a real fight.

Politicians "win" by pandering to voters and interests. So this is an obvious move since they can pander to all those people who grew up being told a cigarette takes a minute off your life while only pissing off some niche industry and a few smokers who are unwilling to vape.

Right, because it totally worked with drugs. People just don't use them anymore. Weed is impossible to come by nowadays.