No one wants to drink or eat from a dirty dish and it's embarrassing when you pull your wine glasses out of the cupboard and they look dirty or foggy! Spots on your glasses are never appealing and re-washing your dishes before serving wine is not ideal. Foggy wine glasses are caused by a build-up of hard water minerals. Since it's so hard to remove the fogginess, it's better to try to prevent it. Wash your wine glasses by hand using hot water then use a microfiber cloth to dry them immediately.
If your glasses are already foggy you can try to get them clean by soaking them in vinegar. This will dissolve the minerals and allow you to effectively wash and dry them by hand. Another option is to wipe them off with nail polish remover or denture cleaner, then wash and dry them by hand.
If the fogginess just won't go away then your glasses may be scratched. Unfortunately, there is no way to remove the scratches from your wine glasses and it may be time to invest in a new set.