Yes, I too see no reason why it should not be checked by default.
But I did find out that feature sure when I first time made Avast as my antivirus, 8 months ago.
Frank, you use too many antiviruses as second hand scanners?
Never missed it much enough, hehe?
I trust Avast for my real time protection, and thus use my Norman as a HD on demand scanner only ,seldom Avast.
But for downloaded program install files I do use Avast quick scan too, even though it has already Web Shield and Standard shield.