Who wants to pay a million plus for an average sized house and have bums taking a dump on your front door?
In fairness, the defecating street people aren’t uniformly sprinkled throughout every neighborhood of San Francisco. If you have the misfortune of living in the urban core of S.F. (Tenderloin/Downtown/Civic Center/South of Market), the street people are very likely to be up close and personal with you.
As you move away from the city’s center, you’ll still find street people in public parks and in neighborhood commercial zones, but they thin out to essentially zero as you get into enclaves of single-family homes or duplexes.