I recently purchased a Curado 100d and after taking the handle off I noticed roller clutch inner tube (part #2394) was missing. Will this hurt the reel if it's missing and any idea why someone would remove it?

It will make the drag on your reel not function as there is nothing to provide pressure from the drag star to the drag disks, it also means that the anti-reverse bearing will not work and the reel if equipped is relying on the anti-reverse pawl to provide this function.

Bottom line the reel will not work without it.

I can tighten the drag down and it works, I looked at the schematics, it is supposed to go on after the roller bearing on the outside of the side plate correct?

Never mind lol, I watched the shimano reel maintenance video on YouTube and figured it out. I was looking stage schematics wrong

The inner tube slides down over the main shaft and rests on top of the drag washer stack, it is also the inner race for the anti-reverse bearing. I assemble the inner tube on the drive shaft prior to installing the handle side plate.

I can't understand how you would have any drag pressure at all without the inner tube.

Like I said I was looking at the schematics wrong, it's there. Thank you sir