I suspect it's a holdover from VHF and UHF operations where contacts are typically more local and "DX" is measured on different scale.
Correct, it's a holdover from WSJT, before the -X was added. Back in those days JT modes were mostly in the "domain" of EME operators and other VHF/UHF pursuits.
Then came Joe Large, W6CQZ. WSJT was a somewhat "complex" package, W6CQZ released JT65-HF, a much more user friendly version of WSJT and targeting HF operators. It was thanks to it that I got involved with the JT modes.
W6CQZ stopped developing JT65-HF, but the "torch" was then taken by HB9HQZ.
It was around this time, or a little later, that WSJT became WSJT-X, and a lot more user friendly.
From then on lots of discussions went back and forth, not always nice. I had had enough with some of the "antics" and stepped back to become just a "dumb" user.
Then came JTDX, and it's what I've been using since then. If memory serves, some of the changes that were later added to WSJT-X had its beginnings, or evolved, with JTDX. The JTDX developers were more open to suggestions, in addition to focusing on HF only.
Today there are at least 3 or 4 others forks of WSJT-X out there. Test them all. Use the one that suits your interests.