It makes life easier for us on later streets. We probably have the best hand. However it's voulnerable so we bet to protect it. Also, by betting we narrow down villains range somewhat (if we check and he bets it gives us no info but costs us the same) which makes turn play easier. The avarage 25NL player isn't aggro enough for us to see a raise here that often.

All other lines suck IMO. check/calling leaves the initiative to him with a lot of potential scary turn cards.