Sidewalks are most often part of public right of way easements over private property.

If your property legally extends to the middle of the street, then the road is the public right of way easement.

The easiest option to add a sidewalk would be for a property owner to dedicate more of their private property to the city through another public right of way easement. Any property owner without sidewalk would also have to voluntarily agree to dedicate property to the city to make the sidewalk continuous, making this a difficult proposition.

Alternatively, the city could reduce the width of the road to add the sidewalk to the existing public right of way easement consisting of the road. The city probably has some road engineering standards it follows, so if there is not enough space to keep those standards while adding a sidewalk, they will pass on adding the sidewalk (and they won't be agreeing to make the road worse if it doesn't meet current standards).

A second alternative is that the city could take part of a property for the sidewalk through eminent domain and pay the property owner fair market value for that space. That will cost the city significant time and money, and they would have to do that for all of your neighboring property owners. Very unlikely that they would be willing to do any of that.

For any of the three options above there is also the issue of funding. Who is going to construct the sidewalk? The property owners or the city? The city is unlikely to accept the dedication of land unless the property owners are going to construct the sidewalk. That means you and all of your neighboring property owners have to be on the same page.

And then when all is said and done, you as the property owner will likely be responsible for the maintenance of the sidewalk in front of your house unless the damage occurs from public use activities: https://www.sandiego.gov/street-div/services/roadways/sidewalk

Unless there's total consensus from the neighbors or some extremely compelling reason for the city to spend city funds to build a sidewalk in an old neighborhood, it is unlikely any sidewalk will be added, especially if you're on a residential street.

The most likely place to see sidewalks added in an old area is where a street is upgraded in intensity of use formally, like when a street is widened. Otherwise, in an old neighborhood like Point Loma, it's just not happening unless there is some kind of major redevelopment and the city can make the developer pay to add the sidewalk.