There has always been litter, but it does seem that the amount of roadside crap is way higher now than 25-30 years ago.
I suppose there are lot more people in the country, a lot more cars on the roads and a lot more packaged “convenience foods”. Most of the litter I see are “meal deals” (drink+sandwich+crisps), take away coffee cups or energy drink/beer cans. Plus the occasional dirty nappy, bag of human excrement or bicycle inner tubes hung from trees.
(Detailed observation based on spending two hours getting 6 dustbin bags of crap out of 200 yards of country lane on Saturday)
I think councils used to try and litter pick along roads, but I’ve not seen anything like that for ages. I suppose they don’t have the money any more.