Steam reviews are simplified so it works like this:
Thumbs up - I recommend you also purchase this
Thumbs down - I can't recommend you purchase this
There is really more to it. And more that results from it.
Just think about it. When do you thumb something down? When it is really bad? Or when it is just not that good?
Up is good, down is bad, that's what it really comes down to. But there is also the middle thumb (and any angle in-between).
As Valve/Steam itself interprets it, they aggregate those recommendations to result in a game review rating like "very positive", etc.
They very much DON'T say "50% recommend this game". They literally say "mixed reviews" - a recommendation and a review are not the same thing, though.
One is deeply personal, the other can strive for a higher measure of objectivity and detail.
Steam makes people give recommendations (or not), mandatory, and also write a review (optional, or at least you can keep it very short), and then in the end combine it into a review score.
Which ends up rather weirdly with games that might be fine to have super low rating or games that are also not that great to have super high ratings. Which in turn is really bad for developers (and gamers that might be missing out).
It's a problematic system no matter how you look at it.
Which is why I wish Steam would move away from that oversimplified system and demand more from people who want to leave a review. If that would result in less but better reviews, awesome!
But hell, as I said, just adding one more option (the middle ground) would be a major improvement.
The reason being, I've not once seen anybody complain about the low hour positive reviews in this thread.
Someone who has spent 100+ hours with the game is far more qualified to provide an opinion than someone who has only spent an hour with it. The latter doesn't get criticised because they gave it a thumbs up while the former will get criticism due to giving a thumbs down. Make it make sense.
That's not really the topic here, which is why you don't see it that much.
I don't think anyone would say that 1h positive reviews are better or more qualified than 1h negative ones. I'd even say it is the opposite!
The only argument I could see is that an unqualified positive review does not unjustifyably damage the developer.
It's not that harmful, therefore people don't get that upset about it?
Plus, negativity simply attracts more attention than positivity, that's just human nature.
But yeah, both are generally bad.