I have a 25 year old Sears Craftsman drill press, with a #33 Jacobs Taper on the spindle. This particular design has a threaded retaining ring, to hold the chuck on the spindle. I have a shaper cutter holder that fits the taper, and the retaining ring. While the shaper cutter holder does not work as well as a regular wood shaper, it does work, I put tounges and and grooves on a lot of scrap lumber for shop shelves.
Never tried milling with it, as the downfeed is not very precise, and the spindle travel lock is not very substantial. The spindle is likely to move as you are trying to mill, spoiling your accuracy.
I have seen the same feature on drill presses described in older Delta catalogs.
I have swapped out the Jacobs chuck that came with the Craftsman drill press for an Albrecht. It made an improvement. When I got my used 17" Delta, the Albrecht chuck went on that, instead of the small Jacobs that came with it. It reduced drill runout, and made the drill press a bit more precise.
IMHO, I think a good chuck is worth the money, even on an inexpensive drill press.
Thermo1