This really came about because of monopoly power and it takes time for things to change.

Here's some pseudo-history to illustrate a point. Imagine living in a city like New York a hundred years ago. There are a limited number of theaters and you can't have infinite theaters and potentially can't even have enough theaters to keep up with demand for people wanting to see theater shows. Why? It's hard to get contiguous land, current theater owners oppose planning permission for new theaters, etc. These theaters rake it in on high margins since the supply is restricted compared to the demand. They also have power over the actors since there are more people who want to be actors than there are acting positions and so they exploit them for low wages and/or poor conditions. Even if you're an electrician and you're getting paid market wage, you're annoyed because the theater owner is raking it in due to their monopolistic/oligopolistic power in the market place and you want in on some of that fat margin. So, you form unions to get in on that fat margin. The theater owner can afford it because you're now both exploiting the theater going public. Under better economic conditions, theaters wouldn't be able to charge so much and there wouldn't be the margins to support above market wages.

The same is true in film and TV. There are again limited theaters to show movies and the theater wants to make the most off a show so they want to run big ones. This provides fat margins to movie makers. Of course, your need for actors has been drastically reduced making your margins way better than stage theater owners could ever dream of. Of course, seeing those fat margins, the actors want a piece of it. Realistically, they aren't doing something more than stage actors were, but c'mon the money is there and a normal person would want a piece of it. Same goes for television: there were/are a limited number of channels due to licensing.

Programming is different. In many ways, we fight against that economically bad situation. We disrupt markets. Our culture is one where we think you should be rewarded for doing something good for people, not entrenching yourself and keeping others with good ideas and products out. Our medium also tends to be infinite. There aren't a limited number of channels (websites) or a limited number of games that could be created. We can create as much as there is demand for.

In fact, as we look at the entertainment industry and its stance on copyright, we can see how we're slowly killing their old way of thinking. We don't want to watch reruns - make more content for lower budgets rather than restricting the amount of content. We don't want to pay the high margins - we see that the entertainment companies are exploiting us (along with the actors, techs, and others taking their cut of the exploitative margins). We see how it's rotten.

And it's important to note, as others have, that the way entertainment is set up is somewhat like a lottery. There's a lot of actors who spend a decade waiting tables only to give up. That doesn't really happen in our profession. Heck, having graduated from university half a decade ago, the only people I know who have been employed non-stop are CS people. We create good value across a broad spectrum of skills and we get good compensation for it - however, we don't have a lottery. Now, if we artificially restricted the number of websites allowed to exist (or games allowed to be made), those few websites would hire the best (aka, the star actors) for higher wages than they currently get, but many people might be waiting tables, trying to make connections, running white-board algorithms auditions all the time, etc. I mean, I know some people that dream of getting that Google job, but the difference between the somewhat low-end in CS which offers a higher than median income salary with good benefits and Google isn't the difference between waiting tables and being Liam Neeson.

And, frankly, getting a union like SAG wouldn't help us in the way SAG helped actors. It helped the actors because the movie companies were exploiting the public. As such, a union would help the actors get in on the price gouging and if they asked for a lot, the movie companies could raise prices a bit. The companies we're working for usually don't have margins like that because it's easy enough for another company to come in and offer the same service at a lower price. Like, a search engine couldn't charge you $1 per search because Google, Yahoo, etc. are free. If Google started charging, you'd just use Bing.

I know how nice it would be to live in a situation where you got higher margins for your work, but in the end someone has to pay that: the general public. That only works if you restrict people from competing and make the supply scarse. Culturally, that isn't us (we prefer disrupting these types of situations) and economically, we wouldn't be able to pull it off since we don't have the history of barriers. I know, I sometimes pine for the lack of competition that lawyers, doctors, actors, etc. enjoy. But ultimately, that even comes at a high cost to them: once you're in, it's great, but on the outside actors have a hard time breaking in, doctors have to go through a decade of schooling, and law school basically tortures its students. Because we operate at the margins we operate at, people can't force us to bow down to them: we can wear what we want, often get flex time, and usually get and keep jobs on our ability to do the job (at least more than many professions).