Broadway has always been influenced by pop music of the time period, and in general, roles written in a low baritone range are much fewer than they were in the days of Rodgers and Hammerstein, etc. since tenors belting high notes is what has made up much of late 20th/early 21st century pop music. We bass-baritones just aren't that popular (and maybe we never were to begin with).
Many high/lyric baritones or "baritenors" have played Sweeney Todd however. In the last Broadway revival, Michael Cerveris was really scraping the bottom of his register to do it, and even spoke some of the lowest notes. Cerveris is borderline tenor, but Josh Groban is very much a baritone - his passagio into his higher register is probably around where mine is, at about Eb4.
P.S. Billy Bigelow actually is a high baritone role. "Soliloquy" is sometimes transposed down, but as written it requires a solid G4 and a sustained F4 on the last note. Billy's other songs have a similar tessitura. It often gets cast with a tenor since it's written right on the cusp of the two voice types.