Okay, but the issue isn't "who is being restricted", the issue is "what are you being restricted from doing". The mere fact of being restricted is irrelevant. Steam could restrict my account right now, but if the restriction was that "I can't launch games whose titles start with Q on Sunday nights unless I spam a Meat Boy emoticon on my own profile page's wall and buy at least $0.14 worth of animu background images", then that's not a restriction that's actually going to impact me, so unless I'm just yelling because they call my account restricted instead of calling all the non-restricted accounts "Premium" or something, then there's no reason to continue the conversation.
Consider your girlfriend, and imagine she hadn't purchase BoI: Rebirth. The major limitations she'd have would be that she wouldn't be able to add friends, they'd have to add her. Is this a limitation? Well, you clearly have a valid account, so it's not impacting her ability to be friends with you. Does she have a lot of friends on Steam that don't have valid accounts and now they wouldn't be able to add each other? Okay, the next major limitation would be chat limitations. She can still chat via the client. She can no longer chat via mobile or desktop. Well, if she's on desktop, she can run the client. So that's that solved. That leaves mobile. Who does she chat with on Steam that she doesn't know IRL? She could use SMS or other chat programs on her phone. I'm assuming she doesn't primarily talk to you through Steam's awful mobile app, right? What else... she can't sell items on the market. This is a negative impact, I guess, but is it really such a problem for her, rather than buying games on bundles, buy her next game on Steam? The market isn't necessary for anything, it's basically a loyalty discount. Hell she can still use Steam Wallet credit (which would get her account unrestricted) to BUY market items, so it's not even impacting her ability to consume content, just profit off it.
And then, finally, we might imagine that your girlfriend is seriously inconvenienced by this stuff. Is she also unwilling to buy a game? Or at least put down $5 in credit towards buying a game in the future? And you're not willing to give her $5 to buy YOU a game, or do so in the future? It's not like they're charging a $5 fee or anything. They're just asking that at some point in your time on Steam, you spend at least $5 on something, including stuff that's 99% discounted.
This is my issue with the complaining. People seem to be bothered, conceptually, that they or someone they know might be restricted, but unwilling to consider what the restrictions are or what their options are for resolving them.