The reason sidewalks are there and not there is simple. Money and politics.
Most of the houses that don’t have sidewalks were probably built before the city required homeowners to put in sidewalks when they built their houses. In some cases the homeowners had to put in their own roads, though in most cases the city has since taken over repair and upkeep.
So the city can’t force those homeowners to put in sidewalks. The (grandfathered in) homeowners have to agree to pay (a fee/surcharge/tax) for the sidewalks (the places where there are sidewalks were either homes built later and the city required they put in sidewalks or the the homeowners decided to put in sidewalks).
Now we come to the politics part. Most of the those homeowners who’ve been around the block a few times, want the city to upgrade the sewage lines and the utilities to put their lines underground/and or upgrade those that are, before they put in sidewalks.
Why you ask?
Well let me tell you about what happened in Imperial Beach about forty years back. The city wanted to put in sidewalks. My father wanted them to put the utility wires underground first. The city said they weren’t going to put the wires underground till the sidewalks wore out. So my father and other homeowners paid for the sidewalks. Two years later the city decided they wanted to tear up the sidewalk to put the utility wires underground. My father said no, and got all the other homeowners on the block to go along with his petition. They city was stuck because too many people had heard my dad arguing with them. So, if you walk the street, there are still utility poles to this day. The sidewalk is starting to wear out. Maybe this time they’ll put the wires underground first. If someone forces them to.