It's because more and more boys are sitting inside gaming.
I live in a deprived area and have worked with deprived children and children from very wealthy homes. Almost every boy had some sort of gaming device, xbox, PlayStation. This was regardless of family income. I've noticed that many parents like their boys to stay in these days- I know it's always been a bit of a stereotype to worry about girls out on their own, but I think that's changed. Parents fear their boys will be the victims of crime, gangs, mugging. In my area there was a massive campaign about "one punch" deaths. Better to keep them inside on the xbox
The difference was that the well off boys had big gardens, and parents who were able to pay the fees for rugby club or Duke of Ed. So they get activities throughout the year. Whereas the poor boy may have an expensive xbox costing £300, but that's his activity budget for the year (saved up for or bought on tick)
Basically, boys have their need for male groups /competition met by having a kick about in the park. Now it's through call of duty
Added to that, and this is anecdotal- boys in my area walk to school in the morning, stop off at lidl or Poundland and buy energy drinks and bags of cheap sweets and crisps. Family packs. They eat them at break and lunch instead of canteen food. I have lived in this area and worked with the children here all my life and this is definitely a fairly recent thing.
I don't notice it as much in girls. I can't see a girl standing in the canteen and eating a huge bag of Doritos and three choc bars- she'd be whispered about. Whereas when I see the boys doing it, they treat it as a man vs food style badge of honour.
Ditto gaming-it isn't as popular with girls