Because recruits want to play in big games against big name opponents. So playing them shows that you aren't afraid to go head to head with the big boys.
Also, where Tennessee is at right now (young), you can spin outcomes different ways. A win gets you "Look at what we were able to do with such a young team." A close loss gets you "We're almost there, just need a few more pieces to get us over the hump and you're it." A big loss goes "We aren't afraid of anyone. Took a young team to their place and gave it all we got. But we're lacking right now and need your talents." Or something like that. Hell I dunno but Butch would know how to do it.
Also, like 005 said. You're going to tell your team that you know they're going to get blown out so why bother playing? Yeah, good luck with the rest of the season (especially through the SEC) after you've lost your team's respect on that one.