Is it due to convenience , availability of cheap games in sales , extra features in steam or did a rise in your disposable income just happen to coincide with the launch of steam?
For me it was mainly 2 and 4.
The other day I saw a trailer about a game I found visually stunning (Anno 2100? I forget the number), and I checked the price on Steam. It was too expensive for something I'd play once or twice, and I thought of pirating it, but then couldn't be bothered to go through all the hassle. Therefore, I suspect it's mostly convenience.
I wonder if there were less sales whether I would spend more on games, spend the same on less games or simply pirate more.
To put it another way, they never planned to sell 10 million units at $60. They planned to sell 1 million units at $60, 2 million units at $30, 3 million units at $20, and 4 million units at $10. Price drops are the only effective and legal way to do that.
I buy from steam because I don't have to deal with any of this bullshit. It's stress free and easy to use. It's the same reason I buy from iTunes. The only computer game I bought that was not on Steam was Starcraft 2. And that was mostly because of nostalgia and great reviews.
The sales, prices, and income mean I buy more games. When I spend $60 on a game it's an investment. I want more than $60 worth of entertainment from it, otherwise I'll just take the g/f to the movies or on a date. When I spend < $20 on a game, it's on the level of a lunch. If it can last a few hours I'm happy.
When I think about how Valve built their brand, at least in my eyes, it was a two-step process. First, make a few great games (and no high-profile duds). That's your foundation. Then add all the Steam stuff, and be careful to never ever screw me over. EA isn't good enough at step 1, and while they haven't screwed ME over, there are too many people crying and screaming for me to ignore it.
Who else could diversify the digital-distro ecosystem? Maybe Blizzard? Except now it's Blizzard/Activision, and Activision seems sketchy this era.
Maybe ZeniMax? (I dunno what Zenimax is like as a corporate overlord, but if you sum up the brand credibility of all their subsidiaries, that's a lot of credibility! I might not enjoy playing id games any more, but I respect the hell out of them, and open-sourcing all your engines is exactly the kind of trust-builder that an overlord needs.)
"Games I haven't played since I bought them in a steam sale"
Maybe if I was a student again...
or a credit card. a lot of great games on steam are dirt cheap - back when i was a kid that played a lot - because i had the time and motivation - 2-8 euros a game would have been affordable. but games were always full priced - 50 euros maybe?, there weren't really any cheap bargain buckets yet.
of course back then i had neither internet and even if i had, no credit card. piracy was the only option mainly because the games weren't affordable nor obtainable.
nowadays i don't have a single pirated program or game on my pc, but neither do i have the patience to play games.
On an ongoing basis, #3 plays little or no role, but if you count "steam exclusive" as a feature, then it played a critical role in getting me onto Steam in the first place. I wanted to play Natural Selection (original, natch), and that meant I needed a Steam account. Back then I was too miserly to pay for HL1, so a friend gave me a spare serial (I'd argue this was borderline piracy in-spirit). Valve didn't get money from me on HL1, but they've definitely had the last laugh. These days I spend a hundred bucks a month via Steam, and I'm happy about it.
Also lack of time, I would never think of pirating a book or game because one will keep me going for ages. I listen to music every day though so until the streaming services come in maintaining a legal music collection as prohibitively expensive.
Conclusion: even if everyone on hacker news answered a survey on piracy practices the data would be useless because HN is not a representative population for all videogamers.