No gripe at all with when you attempt delivery during the day - I'll be out at work. At a place where I can't (and don't want) stuff delivered to (it tends to go "missing").
The problem I as a customer have is that a lot of retailers use Royal Mail. Who are beyond useless. If I make a special effort to stay in, I get a "sorry you were out card" anyway. And if it's not a timed delivery, it's anyone's guess as to when the item will show up (central city location yet still 1st class regularly takes anywhere up to 10 working days from the same city).
Which means at some point a few days later I have to go and put up with the obnoxious sorting office staff. But not on a Saturday. Only between something 07:00-12:00. Which is inconvenient for much the same reason as why they couldn't deliver in the first place.
However, my corner shop, which was on the corner, and open till late at night would have been ideal.
Well done Amazon, you'll put final nail in Royal Mail's coffin.