autozone

I changed the steering chuck on my scamp, wasn't paying attention when I got it, it's a 70 and my scamps a 74, anyway I have a drag link for a 70 but I need a ilder arm for a 70, found one at autozone for 24.00 but it takes them a week to get parts in, advance can have them that day if you order in the morning or the next day, so why does it take autozone so long to get parts? the reason I'm waiting is because the one at advance is like 60.00
part is probably not at the local wharehouse and has to be shipped vendor direct,,that takes in most cases 2 days but can take up to a week..