IRR/RADB and BGP

Our new ISP is asking that I create a maintainer object in the RADB and associated AS/Routes for us to be about to eBGP peer. This is the first time I've been asked by a provider to do this for something as simple as peering to advertise a couple /24's. I've peered with ATT, Sprint, UUnet, Qwest, Savvis, SBC, and Internap in the past and never had to do anything but have a valid ASN provided by ARIN. Is this just so they can dynamically build their prefix/as-path lists? Why would I need to do this and what advantages are there. Cost to register with RADB is $250/year and I want to understand it before I shell out. Thanks, -=Vandy=-