Yes, sort of. Medieval Europeans really liked their honey. Fresh fruit is harder to come by than you'd expect. Most is difficult to cultivate and has a poor shelf life. However, yes, it was a rare treat. They would have eaten more if they could.
Sweet is a biological trick. Nothing sweet in nature will kill you. If an animal can process sugar, and encounter some, it will often gorge on it.
We are predisposed to go for sweet. Companies understand this and add sugar to damn near anything. And that's one of the big problems; sugar finds its way into pointless places, just because sweeter is better. Even things that are supposed to be sweet, like juice or dried fruit, have added sugar.
Also, interestingly, in the US we have almost no taste for sour. Food from other cultures is usually Americanized by making it sweeter.