On Amazon Prime, for example, if two people try to watch the same episode of “Pretty Little Liars” using the same account, both streams will be frozen and a warning message will flash. But one user can simply watch something else until the first person is done trying to figure out who “A” is.

This feels like a missed opportunity for all these services. It’s the failure to grasp the future of television as a shared social experience online. Sure, we are all scattered around, watching all sorts of programs. But then there are moments, as in the days of old, when we are all huddled together — figuratively speaking — tuning into the same show or event at about the same time each night. These days, though, we are watching through some kind of connected device, whether it’s a smartphone, a laptop or a Web-connected television.

Nor does social viewing have to be around a big event. For example, I watched “Friday Night Lights” all winter on Netflix, along with someone I don’t know who also shares the account. Every time I log in, I can see the last episode that this mystery viewer watched — and yet there’s currently no way for us to chat about our reactions to it. That would be much more fun than bugging my other friends about plot twists and turns they saw ages ago, when the show was first broadcast.

We live in a world of on-demand entertainment, where people can consume programming in many formats at any time. That makes shared, cultural experiences more important than ever. Although we can plow through “House of Cards” at our leisure, all in one sitting, do we want to? Or would we rather tune in to Twitter and follow along to see our friends reacting in real time? There’s room for both approaches, but whatever company figures out how to put them together may very well emerge as the dominant force in television.

“The best content is watched live or near-live,” said Alex Iskold, the founder and chief executive of GetGlue, a social TV application that lets users check in and inform their friends about the programs and movies they’re watching. People have become accustomed to chatting along to big television events while on Twitter and Facebook, so that social component “has to be real time,” he said.