The pilot bearing comes in the kit because you need to replace it at the same time.

It's really fun when you get a kit that fits multiple vehicles... in my case, I got a clutch kit for my '86 RX-7 that came with two pilot bearings. One is for the Rotary N/A cars with the M type transmission, and the other... well, I think i's for B-series pickup trucks. They share the same M trans, but the Rotary vs. pissed-on differences would need a differently sized pilot.