I go VERY rarely to restaurants.
First of all, I find that home cooked meals taste better (my GF loves my cooking).
Second, you serve the portion that you want. Better to start off with a smaller plate and go back if you want. Besides buffets (and how bad is that food), you can't do that in restaurants.
Third, you actually know what's in your plate and you put as much "quality" as you want into your cooking.
Forth, I don't pay for "ambiance". At home, put on some music, break out the candles, dress the way you want (I found out the hard way the restaurants don't allow erotic eating).
Fifth, the wine is double (and more) the price of that in a liquor store.
As stokes said, a lot of restaurants put the emphasis on portion size and not on quality. Surprisingly, this seems to appeal to a lot of people. I'd rather have less of something really good than more of something not all that good.
![Drink up [B-o]](./images/smilies/drinkup.gif)