Hussar
Legend
The same reason nobody plays with a 5 point point-buy - sure, you can craft your PC's stats, but with that low a value, who wants to do so and then go adventuring? 4d6 drop lowest and arrange as desired produces the same general effect as a higher point buy - creating an adventurer-quality PC.
But why higher? That's my point. Why not use a generation method that doesn't swing so badly?
Except it doesn't really swing. It goes from maybe a hair below point buy to well above, to the point where a given character is effectively one level higher.
4d4 would give you a perfectly acceptable spread. I'd bet dollars to donuts that random generation people would hate it. You can't get an 18 that way. And that seems to be the point of random generation. Get those 35 point buy value characters on the table with a nice patina of legitimacy.