I think you are looking at things from your one off PC in a room. The bigger picture thinking on YouTube and Vimeo is that converting to H.265 conversion takes a lot of processing power. A player like YouTube has to convert hours of media per second to keep the service responsive. I am sure YouTube will support h.265 at some point, but they will just accept the format and convert it to their own codec VP9+. Converting to VP9 saves a company like Google tons of MPEGLA fees.
Vimeo on the other hand works to try and stay in business by having just that little bit more than what the biggest player on the planet has. That plan has been successful for them, but not so much that people flocked to them. Online posting still comes down to having your video hosted on the 2nd or 3rd biggest search engine. Vimeo sits out there hoping google indexes them and lets people know they have something to watch.
I just googled “short films” and Vimeo does not appear until the 6th result. You would think for certain genre they would pay for top position even if its an ad slot. Vimeo is really more about selling the filmmaker a shovel, and leaving the hard work up to the content producer.
Uploading to videos to YouTube, your content will always be recompressed to a DASH format in .264 or VP9. So uploading larger Professional codec to them will give you the best picture quality. Let Vimeo or Youtube throw away what is not needed, and let them sample the best image you can provide them within reason. If you think that uploading XDCAM, AVC-intra, cineform, dnxhr, or Prores to youtube will take to long, then you need to bust out the wallet for more upload bandwidth.