Everybody has an elections office that's functionally a drop box, though that doesn't necessarily work for people working a 9-5, and that one office may be quite a hike for some people. But yes, 33/67 don't specifically have drop boxes, and another 20 only have one. Philly (10), Allegheny (4), Delaware (4), Bucks (3), and Centre (2) are the only counties with multiple elections offices.

Those with multiple drop boxes: Delaware, 37; Philly, 23; Montgomery, 18; Chester, 13; Bucks, 11; Allegheny, 9; Centre, 8; Dauphin, 7; Monroe, 7; Northampton, 7; Lackawanna, 6; Lehigh, 5; Berks, 3; Luzerne, 2. Biden won them collectively 2.51M to 1.60M. Those with one drop box, including Erie and Lebanon, Trump won 510k to 260k. Those without a drop box, including Lancaster, York, Westmoreland, Cumberland, Washington, Butler, Beaver, and Schuylkill, went for Trump 1.26M to 690k.

Edit: Looking through the list, at least 36 "drop boxes" are at elections offices, including all 20 of the counties that have just one drop box. So there are effectively 53 counties with just their elections office, and 14 counties with at least one drop box placed elsewhere, making the partisan divide even more favorable (1.87M Trump-950k Biden vs. 2.51M Biden-1.60M Trump).