First, men are masturbating to easily available Internet porn (and women also to some extend). It's hard to get hard on with a real woman when you have ejaculated to 10x more beautiful and younger girl just yesterday and you have a completely new such girl awaiting you behind a couple of clicks.
Two, women are getting fatter and fatter. Men are visual and a normal girl these days have such a fat asses that you need to look the other way to maintain an erection. Or at least I need to. I tried to have sex with these fat asses couple of a few times (they are easily available in Tinder and typically comply to having sex on first date) but now I rather blue ball my self or jack off.
Either of these problems are not discussed in polite company, so we can expect that nothing will be done about it. Men should quit porn. The urges that will kick in a couple of days will drive them to seek more human interaction. The second part is that as a society we should identify which food ingredients drive epidemic level of fatness. I think sugar is to blame as is also the food industry to some extend that is trying to make food as addictive as possible. People treat some food stuff with same behavioural patters as they would treat cocaine.