I think charliepanayi is right.

While I personally sometimes don't like the fact that the likes of Arsenal, etc field second string teams, I think it makes the League Cup much more open than the FA Cup and often has more upsets, like Bradford's result against Wigan yesterday. And while it might be frustrating seeing my team knocked out by lower league opposition (cf. Brentford and Leeds in recent years) when we do put out second string teams, at least it means the make-up of the subsequent rounds is a bit more exciting. The League Cup will never have the magic of the FA Cup, but I think it can be just as entertaining.