To be very specific (and don't worry if you don't understand this just yet). If you are unsure of what ranges are, or how they operate, go and read that article first. In order to answer this question we will need to understand the concept of ranges. While it's true they may still “win” the pot this way, they are actually losing a lot of money in the long-run by not going for more value. Weaker players often play strong made hands very passively. Both will have the same effect on your win-rate.
Not “value-betting” at the right time can be just as bad as making a horrible call, when you know you are beat.By not betting you risk “losing value” (losing out on money). It's true sometimes you can think about slow-playing your strong hands, but most of the time, the best option will be to bet. If you have a strong made hand you should probably be betting for value nearly always. The goal of a “value-bet” is to get your opponent to call with a worse hand.
