There were lots of PC databases, of which dBase was one of the more popular ones.

So there was a content-layer market for the early PC-based DBMS's, a la someone marketing the early 1980s equivalent of Wikipedia or Encarta?

Yes, but as I recall it was a rather tiny subset of the database market unless one was very forward thinking and had Internet access and/or was part of a BBS community that shared information electronically which put you in the minority of the minority at the time. Financial market data was probably the largest one early on. Mostly individuals and small businesses were just rolling their own solutions and entering the data themselves until the late 80's / early 90's. Larger businesses had many of islands of systems and data but it was nearly all internal or used to generate paper documents... even internally.

Roughly speaking: prior to the 80's one (often) wrote their own programs, prior to the 90's one entered their own data (i.e. for structured content like databases and spreadsheets), prior to the 00's one created their own content (i.e. documents etc.)