We're fine right now, sure, but what about 2008-2009? Barry is getting old, and could be trade bait. Finley is probably with the Spurs one more year, and that's it.
It makes sense to draft a SG, slowly bring them in for a year. And then hopefully they'll be ready next year to get serious minutes. Sure we have other positions of need - back-up PG and a SF, but a SG makes sense too. With this deep draft, we should have some decent picks at 28 and 33. If just one of them works out, then that will help.