Housing here skews old: 66.7% predates 1980 against a national 49.7%. Those 1,744,070 households renovate rather than rebuild, and renovation is the single most reliable generator of hauling work.
44.5% of San Francisco households rent rather than own, against 34.8% nationally. Across the metro's 1,744,070 households that is the largest single source of turnover work: apartment cleanouts, setouts and lockouts, and bulk pickups that recur with every lease cycle rather than arriving once.
San Francisco has 1,744,070 households across a population of 4,645,029. Junk removal demand tracks households more closely than anything else: people move, renovate, downsize and clear out, and every one of those is a job for someone with a truck and a crew.
Where these figures come from
Every number in these paragraphs is a Census figure for the San Francisco metro, compared with the national figure from the same table.