If you only have a low level of cable service with SD (stand digital) and no ON DEMAND, your only options are watching Olympics on NBC channels you can find on your Comcast cable-box, and what they are showing at that time.
This has always been the case. You get the level of service you are willing to pay for.
If it makes you feel better, I wanted to watch some hockey on demand and there are 3 pucks when anyone passes or shoots... I've tried 2 different games now and they both have the same issue. It's almost worse than their Center Ice package that shows only a small fraction of the NHL games in HD....
I have the option of nearly every other program on demand, why not the Olympics? It was possible 2 years ago with Rio.
And 42 years ago I could watch any new movie released a few months later on HBO, Movie Channel, or Show Time. All were commercial free. Old promises long broken.
Times change, and less control by FCC, or FTC. Blame it on some of the people you might have voted for in the past (or current). Also; more competition now due to new modes for tv delivery. It makes it more difficult for: cable, Satellite, or OTA stations, to even supply certain events they just carried even in very recent past.