I suppose it could be a licensing issue. There have been DSC and KT images in the past, but usually only one at a time (and who's to say what MKF's TOSified versions of the Discovery and Buran in this year's edition "count" as, legally), so maybe they require special permission for each modern image. More likely, it's just that there's a lot of Trek, and it's hard to be representative all the eras. My instinct, though, is that it's the talent pool. The calendars, not unlike the novels, have a stable of regular, reliable contributors, and whether they're fan-artists, Trek-alumnai, fan-artists-turned-Trek-alumnai, they all tend to predate ST09, so whatever assets they have, whether they're screen-used or self-made, are also from the pre-modern era. And the newer stuff can be complex for a single person to replicate. I could probably model an attractive and accurate Mushroom Spacedock, but there's no way I could recreate Starbase Yorktown, no matter how much I want to.
Now, there are solutions to this. There are fan artists who've done excellent versions of KT and DSC ships, and have even made those models available. Eaglemoss has commissioned a comprehensive library of high-quality 3D models of every ship ever seen on Star Trek up to the present day, which I can only assume is horribly legally encumbered somehow since no one seems to actually want to use this incredible resource for anything aside from the half-dozen images for the magazine that comes with every ship. I'm not sure how the calendar editors go about recruiting new talent (I'd hoped the open-submission 50th anniversary edition was a step towards that, but I've never gotten any follow-up from that, and I can kind of see why that experiment might not have been viewed as an unmitigated success).
So, in answer to your question, I have no idea. Even if no one (personally or institutionally) behind the scenes involved in the KT movies or the All Access shows wanted to participate in the calendar, I see no reason why they wouldn't keep their fingers on the pulse of the fan community and try to fill out a couple of the months that are currently going to straight reprints of DS9 book covers with some DSC, PIC, or KT stuff, except for an editorial decision (which, you know, I've seen fan-art takes on
DSC and
PIC that fit in with the "classic" Trek look, so that shouldn't be a huge barrier, and there have been enough AU version of the TOS Enterprise in SotL over the years that it's not a philosophical objection to reimagining designs in general).
. Those are STO game models in the render too, not high-res versions.
