From around 1950 all the way through to around 1995, new shows introduced would have an elaborate opening usually accompined by a catchy theme song that
services as an identity for that particular program. The '50s and '60s had lush orchestral music to guide viewers to say "Mom, the show is on!"; joined by catchier, more vocal themes for the '70s, '80s, and early '90s.  However, I believe excess greed for TV beginning in the mid-1990s has caused TV themes to all but disappear; little did I know at the time that Friends and ER would have some of the last great theme songs at the time. Yes, some shows still use some electronic instrumentals (albeit for a brief period), but most stuff just gets caught in the "split screen". With Television viewing in general seriously down for Generations Y and Z, adding new TV themes would really be needed to lure young people back to the sets rather than surfing on Youtube or listening to Podcasts. Of course, I believe eventually the TV and Internet will merge sometime in the second half of the 2010s to benefit the younger generation; TPIR about a year ago already showed such an item as a prize.

And I agree the DTV switch is overhyped. All it is is somewhat better resoultion and having a wider aspect ratio, and TV ratings continue to decline despite the approach of the switch.

with more time being made for commercials the producers had to find time from somewhere... episodes are now shorter. An hour long drama used to be 47-50 minutes.  now they are 41-43 minutes  and a 27minute comedy is now 22 minutes.

one of the places they made cuts is from the opening theme.