Because consumers can't decide what's good for them or society at large, if companies sell products designed to be as addicting as possible.
Following your logic, there should be no regulation in the tobacco and pharma industries either. Surely consumers can decide on their own what they want to put in their bodies. Advertisements don't lie, right?
> If consumers who are human can't decide what's good for them. How will regulators who are also human decide what's good for them?
Because it's their job to ensure the well-being of their citizens. This is not about ability; _some_ people certainly have the ability and self-control to make decisions that positively benefit their lives. But when companies rely on psychological manipulation to push their addicting products that harm not only individuals, but society as a whole, we can't rely on everyone to resist the machinations of billion-dollar companies and make the right decision. And individual decisions don't impact the rest of society, as individuals don't have the full picture as governments do.
I'm not saying that governments are benevolent, or should make all decisions for citizens, but when it comes to Big <industry>, it's their responsibility to protect us from corporations. This often doesn't happen as well as it should, as some governments have a symbiotic relationship with corporations (lobbying practices in the US are a clear example of corruption), but I'm still glad that some governments at least try to do the right thing.
> If someone wants to smoke cigarettes they should do it provided it doesn't interfere directly with other people's lives.
Agreed. But would you agree that heavily restricting access to cigarettes with strong regulations and taxation is a good thing for society? Or would you rather go back to the "freedom" consumers had in the 1960s, with the cancer rates that went along with it?
Why does the government need to decide everything?