Actually, it's harder to pay fast with great control and accuracy. It's just that hardly anyone does it, and it's easier to get by with sloppy playing when you're playing so fast that most people can't hear the individual notes. Especially in a session where several people are playing the melody all at once. You don't even have to worry about ornamentation at that speed! :^)

It is true that a group of people who play together regularly can get much more tight by playing slowly and with control. More importantly, quietly enough to hear everyone else clearly.