I use multitudes and averages. I mean...I can barely say whether I like game A better than game B (answer: "it really depends on the mood I'm in"), so scores I would personally give to games barely matters...and I'm the one with the taste in games I know best!
Likewise: there are some reviewers I really like on youtube, but even so I listen to what they say rather than who they are, so more than a "thumbs up", "thumbs on average" or "thumbs down" barely registers. So I really like steam's system where you can't do more than up or down. Granted: there are times I'd like a "neutral" setting as well, but I prefer it to, say, google's 5-point system. Why? Put simply: then etiquette starts to creep in. Let's say I play a game that is mechanically okay, but I don't like the style or some thing that's important to me (say...perma death). On steam, I just thumb it down and write down my reasons. But on google's store, I would avoid giving one or two stars because I feel you only do that for games that are mechanically broken. But I don't want to award three or four stars to a game I don't like. And it's somehow even worse when a game is nearly good but not quite. Three stars feels like a "better try again next time", which isn't good, so I don't do that. And I also have it happen that I want to rate it below four, but I don't want to drag the review's average under four.
Granted: part of that is also because of the way others review it (google is a mobile platform and typing takes longer, so they tend to be brief). But even so: more than 2 or 3 options just feel MORE restrictive to me than having fewer options...