The main reason to add wax after corking the wine is to reduce oxygen entering the wine through the cork and preserve the flavor and aroma of the wine. It also helps to keep mold out of the cork.
Due to the cost and labor intensity of hand-dipping bottles, you will find wax seals only used for age-worthy high-end wines.
Opening a bottle with wax seal may seem a challenge at first glance, but is actually pretty simple when modern wax seal materials are used.
Just push the worm of a corkscrew opener through the wax and turn it into the cork, just as you would do when opening a bottle without wax.
Then use the levers of the opener to pull the cork out, this will cleanly break the top of the wax seal.
You are now ready to pour and enjoy your wine.