It's amazing how much commercials have crept in. If you watch an "hour long" show from the early 80s, it's roughly 48 minutes. If you watch a similar show from 10-15 years ago, it's closer to 44-45 and in the last few years, it's more like 42 minutes.
I assume it's only going to get worse as TV ad revenue drops faster with more alternatives.
Watch broadcast TV and you'll notice that hour long TV shows are in 1:15 timeslots because they need to pack in an extra 15 minutes of ads. Or the show will have bits cut out like half of the opening, the start and end of some scenes, etc...
I don't find it amazing. 1980 was 40 years ago. For context, the first commercial TV broadcast in the US was in 1941, and it didn't really get going until the late 40s. For the format not to have found it's most profitable show length for an hour long slot 35 years after it started, and for it to still be evolving 40 years from that point with a huge amount of innovation in the tech isn't really surprising.
I would suppose OPs argument is that this is like how much sawdust can you add to food before people notice and choose alternative media consumption. There's presumably a lot of deadweight loss and collusion that play to these results.
Ad revenue has also dropped with DVR use. It's amusing to think about adding 20% of ads to compensate for 20% of viewers skipping over the ads, since it's a race to 100% ads that nobody watches.
I assume it's only going to get worse as TV ad revenue drops faster with more alternatives.