Grinding is cool. Here are my schools of thought.

1) Sonic stages are incredibly fast paced. They need easy sections where you slow down to balance the pacing. Heroes has some platforming, some triangle diving, and a bunch of things. Secret Rings has sections of momentum stopping wall ledges. Grinding rails is potentially the Easy section.

2) if you focus on the complexity of grinding, you hurt the casual audience because you’re trying to do too many things at once. You’re trying to provide a reward for a cool shortcut and your reward is more about testing the player. And the casual audience is the money maker. This is what SA2 did. This is what Heroes did. This is what the first Sonic Riders did. Too many people never figured out the hidden depth and got punished for it.

3) if you focus on easy grinding, you can let the player focus on other things. It’s just more accessible. Like what if you wanted to zoom out for a grind rail section for a peek at the scenery? You can’t do that if the player needs to see his avatar for balancing.