I view 10/10 not as perfect but as perfect as you can reasonably get. An actual perfect would be an 11, which is higher than you go precisely because it's impossible to achieve. There are very few games I'd 10/10.
Plus if you give out no 10s then your 9/10 effectively becomes a 10 since it's the highest rating something can get.
(\/)(\/)|-|
In Zeus We Trust: All Others Pay Cash