Well, actually it may happen even to laminated decks. Sometimes the lamination itself may peel, and the edges of the cards may split due to shuffling. It depends on the quality of the lamination, and the quality of the cardstock.
Nailpolish works, but only if it's not a "workhorse" deck. If you use it and shuffle it a lot, the nailpolish will wear off quickly and leave the corners and edges of the deck unprotected again.
If your deck is not laminated, perhaps you should look for a way of getting it laminated in the first place? I know that some folks here have laminated decks in the past, but I have no idea how...