This just means they've stared to use the full scale.
Users are also more prone to spamming 1 and 10s. I can click on a random metacitic user and 9/10 times i'll find system war shit.
What people don't really understand is that users' scores are more reliable than critics' score for a single simple reason: number.
Yeah many users just give 1 and 10 but when the number is high they don't count, one wrong critic's score has more weight because critics' reviews number is smaller, it's one of the basic rule of statistic science, the higher the number of data the more reliable it is.
Simple and quick example:
votes: 5, 10; average: 7.5
votes:5,5,5,5,10; average: 6
votes:5,5,5,5,5,5,5,5,5,10; average: 5.5
and so on.
Another example? That 2001 list, those users' scores are less fanboystic and more equilibrated.
Another example? Gta4(yes it still burns!) critics' score:98(ps3 and 360), users' score: 7.9(360) and 7.5(ps3), just saying.