Is there deep bass in the HDTV audio spec?

TV shows generally don't put much low bass onto their soundtracks because 99% of watchers listen to their shows through the internal TV speakers and wouldn't hear it anyway.
Interestingly the Weather Channel until fairly recently didn't high-pass their audio, and you could hear not only footsteps in the studio but trucks passing by outside the studio. They must have been using internal TV speakers for monitoring and didn't know the difference.

If you have your speakers set to "Large" and you're watching "stereo" content, nothing will be sent to the subwoofer.

AFAIK, broadcast HDTV uses plain old dolby digital. The one that people could hear all the subbass on Master and Commander DVD, but that had been rolled off on the BluRay. Bass is much easier to encode, afaik, since while you need roughtly 44,000 bits per second to cleanly record 20,000 hertz, to record 20 Hz, you'd need 40 only bits per second (no need for extra bandwidth since you're not brickwalling at that frequency). Whatever bass is in the recording ought to get through the dolby encoding process just fine unless somebody intentionally cuts it off.

I know that frequent participant FilmMixer mixed one or more episodes of the HBO miniseries Pacific. He used the same multimillion dollar mixing stage (great to have a job with cool toys) as he uses for major motion picture releases. I'd be surprised it HBO or anybody else took extra time and cash to change the sound on a movie they broadcast . . . but I've been wrong before.

Is 24 on any more? I get good bass when watching it on Netflix

Every network has the ability to high pass the content wherever they choose to, so you may or may not get the same audio bandwidth as contained on the original source. They can compress it too, so there won't be as much dynamic range, and a lot of those dynamics lie in the LFE content.