The abbreviation makes it clear when you're talking about the specific, distinct product lines that are separate from the mainstream desktop hardware product lines, as opposed to when you are merely talking about a desktop that is high-end in some vaguely-defined way.

But the abbreviation is less useful when the continued existence of the HEDT product segment itself has been repeatedly called into question over the past few years. The death of multi-GPU gaming and explosion of CPU core counts available on mainstream desktop platforms have removed the two main reasons for having a separate CPU socket for high-end desktops. (Historically, HEDT products were usually at least artificially segmented from workstation products; the latter segment is not in danger of disappearing.)