buying beer is so easy anyway, that I just dont see the advantage here.
The advantage is that you can use your BTC without having to change them. This is an incentive for normal people to accept BTC for little exchanges.
10$ for a McDonald and a couple of beers is not much, but 10$ a day for a month is 300$ and 10$ a day for a year is 3600$. So you can make a few extra thousands $ a year with side activities, without regulatory hassles and tax free.