Why did Red Squadron give their call signs in random order?

One thing that has always confused me about Star Wars: A New Hope is that at the beginning of the attack on the Death Star, Red Squadron gives their callsigns in random order.

Red Leader (presumably Red One) asks for everyone to report in. Then we hear Ten, Seven, Three, Six, Nine, Two, Eleven, and Five are all standing by.

This seems like an incredibly impractical way to report in, as it's hard to keep track of whom you have heard from and whom you are missing (indeed, Red Four and Red Eight didn't report in, despite both being present, but I bet you didn't notice that).

Why didn't they count off in numerical order? Something like this:

Red Leader: All wings report in.

Wedge Antilles: Red Two standing by.

Biggs Darklighter: Red Three standing by.

[Silence]

Red Leader: Red Four? …Are you there Red Four?