[Jeff Rodriguez]

You've worked you butt off all day coming up with strategy, coordinating with alliance partners, and executing strategy. You've put everything you have into trying to be #1. On Saturday, you finally achieve that and are ranked #1 at the end of qualification matches, BUT you don't pick first? I'm sorry that just isn't fair to the robots that are #1, 2, etc.
Why would I want my team to be #1 now? Instead, I'm going to try and be #8, even if that may mean losing a match or two.
I'm sure there a plenty of other people that will do almost any/everything to be #1 seed, or in this case #8 seed.

Lets say you have the top 10 teams. The team seeded #1 wants to be seeded 8th so that they can pick first, so they lose a match on purpose. Teams seeded 2, 3, 4, 5 all see how they did this, and they all go out and loose a match to get closer to the #8 seed.
This trend will start to snowball and eventually you will have teams trying to lose more than their opposing alliance.

Why shouldn't the top 8 seeds be able to form the strongest alliance they can?

The problem with comparing a FIRST alliance selection to a pro sports draft, is that professional sports don't have alliance partners. Only one teams wins a championship.
FIRST is unique, and has a unique draft system.