If that's true, then they must not have shown any interest in me over the last year and a half. I've never once seen those prompts, aside from the EULA updates. Which are now called "subscription updates." Call me old-fashioned, but I own my games in full when I buy them.
As for what kinds of data Steam collects, you'd have to ask someone who is a developer or a publisher, or someone who works in the industry for that one. I know a few people who work in the industry, and from what they've told me, devs and publishers have access to a lot of data behind the scenes that Steam compiles for them. Things like...whether the copies we buy are physical or digital according to the keys registered, what the demographics of players are, time spent playing/periods of most activity, if the library of their players has one or more games from a certain dev/publisher, DLC purchased and when, and quite a few more.
Most of this is pretty much harmless, but here's the rub: All of that is marketing data, which you're agreeing to offer by using Steam, irrespective of whether you tell Steam it can collect that voluntary data from before. And what does having Steam open all the time encourage you to do? Spend money, from which Valve gets 30% or more every time, even with massively discounted game sales of 50% or more.
Actually, let me ask you something in return: What sort of benefits can you see from giving Valve a laundry list of the programs you have installed on your computer? Ignore the hardware bit, and just focus on the software part. They can't market Office 2013 to you, nor any upgrades to Firefox. So, why give them that kind of information? Origin may not have asked, sure, but is Valve really that worthy of a list of your preferred programs? And if they are, I'd like to hear your reasons why.