What's the deal with poor TV concert-sound?

Something unusual happened last night, something significantly rare that I felt compelled to mention it. I was watching the 4th of July celebrations on PBS and the concert sound-mix was excellent?! I've grown inured (though still not happy) to the fact that almost all live music on TV has a shitty mix. I'm pretty sure it's because they want to make sure it still sounds decent even on a cheap TV with cheap speakers. They do something similar with studio recordings where they double-check that it still sounds good on a set of cheap car speakers. But I don't think they 'dumb down' the mix the way they do on TV, i.e., entire instruments will simply be missing.

Even the DVDs of concerts will exhibit this. If the band wasn't sufficiently mike'd then they might be stuck making the best of a bad collection of line recordings. But for a concert that's being recorded for resale you'd think they'd have avoided this predictable issue.

Here are 2 recent examples of this dumbing-down:

• The Steve Miller Band - Live in Someplace (sorry, I forget). It's a recent recording and a great performance, but several times I saw someone playing a guitar rhythm or some kind of percussion and it simply was not there in the mix.
• Tift Merrit - Live at Austin City Limits. You rarely hear Tift's rhythm guitar, or even her piano backing. In this instance I suspect they only had 1 line for both the piano and organ, not realizing that she and the organist sometimes play at the same time. And since the organ is much louder than the piano (see my review of her San Diego performance two months ago) they probably had to drop the level to keep it from drowning the mix; sorry piano! And I was particularly excited about this DVD because it included a DTS soundtrack (which is higher-quality than Dolby Digital) so I assumed it would have a higher-quality mix, too.
  

Lastly, the other disappointing thing is that I'm still hearing these dumbed-down mixes on digital surround-sound broadcasts on HDTV. I suppose someone with an HDTV might still have cheap speakers but isn't the likelihood a lot higher than the viewer will have a proper sound system (like me) ?