SoulUnison
Banned
Because the GUN robots set up a defence there.
I could have sworn there were other scenes showing that Eggman/Shadow/Rouge just teleported in and out of the Pyramid Cave Hidden Base at will on some sort of Star Trek-like Transporter Pad. So maybe he just wanted to to take the scenic route?
I always thought one of the weaknesses of Adventure 2 was that they tried to make sure Tails and Knuckles had as many stages as their counterparts Eggman and Rouge, even when it didn't make a whole ton of sense in the story - and then where it really counted, Shadow has the least stages of any character,despite being basically the advertised reason (besides Sonic, of course) to get the game in the first place.
And even having only, I think, 4 stages, you could tell they were kind of stretching to get even that many into the story.
(What was the point of Sky Rail? Shadows chases Tails and in the end...just sorta turns back.)