I completely feel your pain as I too was looking forward to playing my 360 copy of Skyrim on my One & was surprised that it didn't make the initial list of 104 games, yet has been quoted as being in the top 4 requested games. Surely Bethesda wouldn't say no to allowing this to happen seeing Microsoft has indicated that part of this process involves licensing/approval from the publisher.
I think there are a couple possibilities at play here:
1) The initial list were among the "easiest" to certify for compatibility due to some of them being owned exclusively by MS and the others already having the licensing sorted out. We have to keep in mind that this is also for marketing & to help generate additional revenue by encouraging folks to move away from the 360. So the more games they could announce during launch, the better.
2) Skyrim is coming as part of a future list of additional games for compatibility as they've indicated they will be adding to this list over time
3) This is more speculation & hopes on my part, but maybe Bethesda is holding off because they're still deciding on what to do with the nugget of info they made known as part of the Fallout 4 development interview, when Todd Howard told Game Informer how they ported it to Xbox One as a technical exercise to acclimate themselves with the hardware early on in Fallout development. I believe the quote was "Don't get your hopes up just yet" which hopefully means it was stated purposely & indicates they haven't completely written off the idea of pursuing it as a side project between now & the eventual release of TES 6, which is probably at least 5 years away.