Silver's story in 06 is too focused on himself and not enough on exchanges with Sonic. Games with a character arc usually go as follows

>I need to do a thing
>who is this Sonic guy? He needs to stay out of my way
>Woah this Sonic guy is alright
>audience: Sonic is cool and the new character is too!

A simple workable formula that gives the new character plenty of time to establish themselves to the audience and have something to do with Sonic even if temporary. Silver is so detached from Sonic that he may as well be a comic oc