Waiting for Godot (except it's a Zanussi)

I'm waiting for a new freezer to arrive.

It will come - apparently - some time between 9.00am and 1.00pm.

Why can the people who deliver things to go in the said freezer do two hour slots but the people who bring the freezer itself (which is coming all the way from, er, Bearwood) can't be more specific than four hours?

(Update: they've just called to say it'll arrive between now and er, 1.00pm.)

(Later update: it arrived at 12.20pm!)