Personally, I think the wrong question is being asked. The right question is 'why add DLC that doesn't work with VR to a game that has great VR?'
That's a really great question. FDev brought VR content to the table and niched a market with it. VR and the stellar forge set Frontier apart, and still does years later. It was a brilliant move and a cornerstone to Frontier's growth.
I have no idea what the development factors are, but I do know that Frontier does (or did, 2022 fiscal year could be difficult) have the cash on hand to develop it. In the end, putting the money in the bank is going to cost them vastly more than sinking the cost into developing their product.
As a VR player, I can't imagine playing ED otherwise. I've resigned myself to Odyssey with the hopes that they'll develop VR, understanding that it is a growing market. I'm still waiting for that "Armstrong moment". Not only that, as a customer I still see "No VR at launch" as saying, "We intend to develop VR for our VR game at some point".
I can understand a bottom line sentiment such as, "the VR player base is a small subset, so it's not worth the development cost". I just find it short sighted. VR Odyssey would solidify Frontier's market share. Which has greater marketability and potential longevity, a garden variety fps dlc? Or a native VR dlc (added to an advertised VR product) with combat, exploration, and discovery set in the ED universe?
There's a lot of reasons for Odyssey's poor reception within the gaming community, but one of the biggest is that they moved away from what made them unique. Developing ED is not about "what we can't do", its success lies in realizing what can be imagined.