Does the US currently issue independent B1 or B2 visas, or only the combined B1/B2 visas?

I know the US has these two most common visa categories:

• B1, business visa
• B2, tourist visa

^{(This question is not concerned with the other visa types.)}

I also read constantly about a B1/B2 visa, and Wikipedia confirms that the above are usually physically issued in a combined form:

In practice, the two visa categories are usually combined together and issued as a "B1/B2 visa" ...

This makes me wonder if there are also dedicated separate physical visas that are only B1 or only B2 visas.

If those do also exist, what set of conditions, roughly, would lead to the issuing of one of those rather than the more common combined visa?

If they do not currently exist, how recently did they formerly exist in the past?

^{I got thinking about this while tagging questions that discuss B1/B2 visas and wasn't sure how to tag the questions that only mention B1 or B2 visas.}