It can't be made illegal - our roads would clog. We live in a country village in an agricultural area. The average Combined Harvester measures 3.8m wide - we have others that are much bigger and the road is 5m. wide. One tractor plus its accoutrements the other day only just cleared the cars parked half on the pavement - it was a tracked vehicle and had to occupy the whole of the pavement on the other side of the road. The bus service has just closed and there is no shop in the village. Nearest tiny shop 2 miles.
It is also a straight road off a downwards hill and we have a speeding problem, so people park half on the road to create chicanes to slow speeders down. (No, the Highways authority won't accept we have a speeding problem and we all have 30 signs on our wheelie-bins to try to slow traffic.)
Everyone is very considerate and leaves room for push-chairs etc.. We now have to have 2 cars in most households and one of these has to be parked on the road. If this car were not half on the pavement then the road would block - simple as that.