Wine is also so easy and cheap to make at home. The only reason to buy commercial wines is if you're picky about the specific flavours. How many people do you know that are that picky? Pretty much everyone I know enjoys some wine on occasion and not a single one of them care about what kind of wine is served.
I've made beer at home, and it's easily possible (with practice and determination) to make beer at the same quality as almost anything commercially produced.
Only once in 40 years have I tasted a homemade wine that would stand up to a good $10 bottle from the liquor store.