[2022] More zombies present in cities......

Turn on Feral Sense in the save options if you haven't yet. There's actually usually a moderate to large amount of zombies just roaming around, but their senses are too weak to find you most of the time. Feral sense changes that and makes it so, if a zombie is nearby, it's pretty likely to notice you.

Also to note, slaying zombies in a given area can/will clear it of zombies for awhile. So, whatever is your most trodden path will definitely have fewer zombies than a place you haven't been yet.