Because the hand would be a lot less interesting otherwise.
I have only been sitting with this villain for two orbits but during that time he has been opening a LOT of hands PF. I do not yet have a read on his post flop play.
Poker Stars $2/$4 Limit Hold'em - 6 players - View hand 428434
The Official DeucesCracked.com Hand History Converter
Pre Flop: (1.5 SB) Hero is CO with Q
K
UTG raises, 1 fold, Hero 3-bets, 3 folds, UTG calls
Flop: (7.5 SB) Q
2
3
(2 players)
UTG checks, Hero bets, UTG calls
Turn: (4.75 BB) A
(2 players)
UTG checks, Hero...

. Given all the worse hands that probably will call (I assume he calls 5x-2x, FD, Qx that was waiting for the turn, PP, broadways), Im laning towards a valuebet in this case. I wuld bet again on a safe river.