Because content providers are greedy. Actually there’s a bit more to it than that but yeah. That.
DIRECTV’s on-demand system dates back almost ten years. It was one of the first nationwide HD on demand systems, although other providers had on demand in SD in larger cable systems for several years. It came long before Hulu and other ad-supported video-on-demand systems. This is just one way it’s showing its age.
In order to get on-demand content from some networks, DIRECTV had to promise that viewers couldn’t skip the ads. Ad-skipping was a huge concern in the late 2000s as DVRs began to take over and making non-skippable ads was a big priority. Giving content providers the confidence to know their ads would be seen was a big “carrot” in getting them to approve nationwide, HD on demand. So, the lawyers all got together and decided that much of the content on DIRECTV would have non-skippable ads. Unfortunately given the constraints of the technology back then, it also meant that since you couldn’t fast-forward through the ads, you couldn’t fast-forward through the program. It was a big sacrifice but it made all the big boys in the boardroom happy at the time.
Another reason fast forward was disabled at the time was that most people could barely manage to get a standard definition program in real time. I remember the rule of thumb at our home was, you could watch on-demand programming in SD about 5 minutes after you requested it, but you had to watch 25-30 minutes to get it in HD. Taking fast forward out of the equation meant that you’d have a much better experience and wouldn’t be stuck buffering
So here we are ten years later, more or less, and on-demand still works about the same. Of course now you have Hulu and other apps that let you fast forward through the content and not the commercials, and you think that’s pretty normal, but DIRECTV hasn’t really updated that system to let you fast forward through content but keep the commmercials. I don’t think they will, either, because chances are people aren’t really annoyed with it. People do still watch on demand because it’s convenient, but since most on demand content is also available from provider apps (which are unlocked when you are a DIRECTV subscriber, you can find it another way if it really bothers you that you can’t fast forward.