Brick fence posts (or pillars) lining property without a fence

They’re there in case a car runs off the road and runs into the brick post instead of the house.

how far a part was each post? probably for random cars getting in the yard, etc

Probably was a deteriorated fence material that was removed. I see them like this sometimes. Some have wired between the columns and grown some great greenery boundary.

The houses are probably a few hundred feet back from the road, and the posts are at least 50 feet apart from each other.

A way to visually demarcate their property frontage/lot size. Those properties have some pretty long frontages and it wouldn't be readily apparent that all of that lot belongs to said rich person. I think an ornamental metal fence would be better but it would be very expensive.