I'm lucky enough to live in a rural, litter free area. But I'm in the larger towns and cities enough to see for myself what you are talking about.
I seem to remember a few years back (maybe when litter laws & associated fines were updated?) in my parents' local, large town paper, that rarely a week went by without someone being fined for littering - and the town did seem to improve for a few months. But then the spate of fines seemed to fizzle out and they are back to square one.
Faced with a particular localised littering problem, my parents were advised to install CCTV to catch the culprits - it wasn't even my parents property! Occasionally a litter warden would arrive and clean up but now even that seems to have stopped.
It looks to me that in the local authorities you have people who are office based - doing very little, and then a lot of "jobsworths" on the street who seem to be be only willing to empty the already overspewing bins.
I can't remember the last time I actually saw someone sweeping the street.