I think it boils down to personal preference. I like peanuts and cashews roasted, but not salted. You obviously enjoy them with salt. Some foods do taste better with seasoning, especially salt, such as fries. I think we enjoy them with salt, though, because we have eaten them or been served them with salt the majority of occasions in which we have eaten them. Therefore, when they aren't salted, we naturally prefer what we are already used to.

"Table salt (sodium chloride) is used as a flavoring agent in the cuisines of many cultures. Despite health advisories, maintaining a no-salt or reduced-salt diet has proven difficult for many. A common complaint is that foods taste bland and insipid without sufficient salting. It is widely believed that salt intensifies the desirable flavors in food. For example, salting a slice of watermelon appears to make the watermelon taste sweeter. Another view holds that the value of salt is in its ability to mask undesirable flavors, and in this way, the food tastes better. This laboratory exercise investigates the effect of salt upon taste by using a simplified model. The students participate in a blind taste test. Bitter (e.g. urea), sweet (sucrose), salt, bitter/salt, and sweet/salt solutions are prepared prior to class time. Invariably, bitterness is no longer detected when the salt is combined with urea yet the sucrose /salt solution is always ranked as not as sweet as the sucrose alone. Salt is shown to make food taste more palatable by suppressing unpleasant flavors." http://www.zoo.utoronto.ca/able/volumes/vol-20/mini12.mcmahon.pdf