It's a shame that nowadays everything "needs" a phone number. I just put in a proper prefix code and then all zeroes as a number if some company forces me to. That works for some of the websites. Some stores even print that on a shipping label. So it might supposedly be there for a reason. But I've never heard this helps if a parcel gets lost or something. They won't call anyways and the real reason is they can store it in some database and depending on the exact business do all kinds of other stuff with it.