Currently, TV Company X makes a bunch of shows and airs them in the US. Some of them make huge amounts of money, some fail miserably, most are somewhere inbetween. You make money in the US either by selling your content to networks, or putting it on your own network. The networks make money out of selling subscriptions (B2C) and advertising (B2B).
Internationally, you sell your content to networks in other countries. These will be whole bundles of content - let's say 5 shows, each with 3 series. This is a purely B2B business model, with guaranteed future income. Once the local networks have licensed the content from the producer, they promote it and sell their own advertising and subscriptions.
It seems that you're suggesting they replace that international model with one where they sell content online direct to consumers. The producer now has to take over all the marketing of the show, and sell its own advertising. They will also come up against local competition who are now making their own shows. And they've got to build websites with payment systems, and offer customer service. Oh, and deal with local regulators.
It will take a very long time to set up that new business model, and while they're doing it, they've lost all the guaranteed income of just licensing it to local networks. Their share price tanks as a result, and they have to deal with Carl Icahn launching a takeover bid.
Then there's the evidence that the number of people who will pay to consume large amounts of content online, while still accepting advertising, is still relatively small internationally, because not everyone has the technical capability or inclination to do it.
That is why it loses a huge amount of money in the short term. TV producers can't say 'iTunes or whatever'. They have to hire departments of people to build cashflow forecasts and business models that they can justify to shareholders. And if the CEO of TV Company X turns out to be wrong, they've lost their job with the $10M per year salary.
In the long run, it probably will be the case that TV will be distributed like you say - aired through the internet, pay-to-play. But if it's not happening quickly enough for you, then just download the torrents. It's more profitable for TV Network X to ignore the money you're offering than to change their entire business model so they can accept them.
That model has been a disaster (for music companies) as they take all the risk for the failures, while Apple gets a relatively large proportion of revenue from the winners.
For the owners and shareholders of TV networks, solutions tend to fall in one of two mutally exclusive groups:
Option #1: Take advantage of all these people who say they'll pay. In the short term, you'll probably lose a lot of money as you cannibalise your existing business model. But it does give you a moderate chance of long term survival.
Option #2: Keep the status quo. In the short term, you'll continue to be mildly profitable, though your long term survival is unlikely.
Since markets reward short-term behaviour, the first option is career suicide for any CEO. While the second won't mark them out as a visionary, it will guarantee them a large salary. What would you choose?