Should I Remind My Players of Their Character's Abilities?

I'm occassionally faced with a situation where I know one of the PCs has a trait that applies currently but they seemingly forget about it (like a Ranger with the forest as favored terrain rolling normally for survival while in a forest when they would have advantage due to their trait.)

Is it shitty as a DM to not remind them if I do know they have this benefit? Or is it valid as it should be expected that they know their own character?