And by 'traditionally', onlyonemac means 'on the IBM PC and PC/XT, and hardly anywhere else'. The ROM BASIC was one thing that hardly any early clone manufacturers bother to implement, as the whole idea of having a ROM interpreter was sort of a late 1970s thing that was already becoming a thing of the past when the
IBM Model 5150 Personal Computer came out in late 1981. It was considered too much work and too much risk of infringement to bother with.
In any case, it was hardly worth having by then - it was mainly used in systems using cheap
cassette drive storage, which didn't need a full operating system to interface with, but those were rapidly falling out of favor as
5.25" mini-floppy disk drives dropped in price, pushing out both cassettes and
8" floppies. While the 5150 had a large DIN connector for a cassette drive (similar to the original keyboard DIN, and often mistaken for it), I would be surprised if they sold even one cassette drive system, and AFAIK all original PCs sold had at least one full-height 5.25" Double-Sided, Double-Density 360KB floppy drive.
When you consider how impressive that amount of storage was at the time, it isn't surprising that the cassettes, which were much slower and held between 64K and 128K, fell out of favor rapidly. The interrupts for both ROM BASIC and cassette drive interfacing were rapidly re-purposed starting with the IBM PC/XT, and no one has used either of them for their original purpose since.