Try doing the sums, there is only a small saving on the monthly payment on a 30 year vs 50 year, but the overall payment to the banks is hugely increased, that's why they want to push them.
Morals have gone out of the window for most people, people would cheer anything that is good for house prices even if it is terrible for young people, just because it improves their house prices.
It's a terrible idea but not enough people will have the courage to say it, much like virtually none of the mainstream media will ever say anything bad about stuff like HTB or SO, despite these being very poor products for most (not all) of the people that take them out.
If you want to make houses more affordable, just don't do any props or suppress the price of money and the market will correct to a new equilibrium.
Let's be honest, most people don't want a new equilibrium even if it is better for the young because that involves lower prices.