I find it pretty hypocritical that the same people who push for e.g. legal marijuana would go for banning social media apps. Don't get me wrong, I use neither and think both are mentally, physically, and morally corrosive. I would not care to have either present in the community where I live, nor for my future children to use them.
That does not mean it is the province of the state to ban them.
weed isn't designed to be addictive. You'll find most people would be cautious about legalising heroin, meth or crack.
To give them some credit, they support both positions because they were told to support them by the same people and never put much thought into it.