I sometimes wonder if it wouldn't be better to simply tax internet subscription revenue, and divide up the proceeds according to download statistics.
And taxing internet subscription revenue is a terrible idea. Many people who pay for an internet connection do not pirate media, and in fact don't rarely purchase media whether physical or digital. Taxing these people for something that they don't want is unfair.
Piracy is something that will always be around but the way to tackle it, imho, is to make obtaining it legally a more attractive option. Steam is a step in the right direction; if you pay for a game then you get a number of benefits that you otherwise wouldn't have if you pirated it.
And if there are other uses, e.g. remote work over VPNs, specific contracts with remote locations, etc., such traffic could be exempted from the taxable cap.
One thing I'm pretty sure of: trying to sell information (i.e. bits) along the same lines as historical tokens (DVDs, CDs etc.) is doomed to failure. Steam comes with several major drawbacks: you need to be online regularly to log in, you have to put up with a client on every machine, forced advertising, higher prices than the shrinkwrapped box (the case here in the UK), etc. It's also a single point of failure in a business sense - size or past profitability is no guarantee against overreach or future bankruptcy, and the more eggs you have in the Steam basket, the more you have to lose when (and it will eventually) it goes away.
Re pirating internet access: that's inherently different, because (most) information is a non-rivalrous good, while access to a network pipe is rivalrous.
You're right. In the past (and probably ongoing now), there have been plenty of people illegally hooking up cable Internet and satellite connections. It's just not quite as easy compared to the price for most people. Heck, I'm ready to pay a lot more to get a much better service that they won't offer me..