I think the supposed "lack of interest" of the SD4k boils down to its value proposition. 2 main points:
1) If you're going for a more "vintage" piece, the earlier SDs can be had for less than 10k (unless you're talking about rare unicorns like the legendary Double Red or other early vintages)
2) For a modern Rolex diver, most people go for the Sub because the differences between a Sub and the SD4k may not be significant enough to justify the price diff (10k for a Sub nodate VS 14k for a SD4K). From a pure aesthetic point of view, there are very little differences between a modern Sub and a SD4K, and 99% of wearers won't need the diving upgrades (extended clasp, more water resistance) anyways.
For me, I went with a SD4k because of the following reasons:
- I like the extra thickness of the case (but yet still within reasonable means unlike the DSSD) compared to the Sub. The case just has a balanced substantial aesthetic to it.
- Date function without the cyclops (best of both worlds IMHO)
- I like the full minute graduations around the bezel.
- I prefer a modern piece with ceramic "bling" bezel.
All in all, it's just a nice balance / in-between of the Subs and the DSSD, and checks off the boxes in 1 nice package for me.
In fact, I wear it so often that it has become my daily beater (almost).
Couldn't have given a 2 cents worth on the SD4k better myself! I'm glad I ditched the idea of the DSSD because of the thickness (not as versatile as SD4k and the Subs), so it can't fit well underneath a cuff when the occasion calls for it.