Because Utah has consistently struggled to bring in quality FAs. Especially young players that have a bad perception about living in Utah. If rookies chose their team Utah would be low on the list of teams chosen and we would have to overpay to get kids to come here like most small markets would have to. Big markets and hometowns of kids have an advantage. Lots of kids make friends as well early and would try and team up early as well to make super teams.
Have the Jazz struggled to brig in quality FAs? What teams have huge track records for attracting free agents? The Lakers getting Luol Deng and Mozgov? The Knicks getting Courtney Lee? The Jazz beat both those teams in quality this past year getting Joe Johnson. Most young FA's don't leave their original team because they are restricted, then if they are really good, they usually stick with their team because they can pay the most or they leave to the top contender to form a super team. In recent memory the All-Star caliber players who have switched teams in recent years via FA are Wade, Lebron, KD, and Aldridge. I'm probably missing someone, but none of those moves were based on market size. Lebron went home, KD went to the best contender, Aldridge went to a quality franchise to win, and Wade went to Chicago because they offered the most money and is his hometown. Joe Johnson could reasonably be put in the same tier as Wade this year and he chose Utah (actually I think most would agree JJ was the better/more impactful player this year).
The pool of UFA is usually really small in terms of quality, and most of them stay on their original teams. There isn't that much FA movement in the NBA. The needs and desires of rookies is going to be much different than NBA veterans. Teams making rookie "super teams" doesnt really worry me at all. I dont think most NBA teams would want to do that and I dont think it would be a good situation for most rookies and would have a low success rate in terms of winning in immediate and in the future (though I would love to see some team try that, it would be a cool experiment and a benefit of the system).
I think people are really undervaluing the reputation the Jazz have among agents in terms of player development and how big a role that would play in getting rookie free agents. At the end of the day, the Jazz have a better chance at getting a top rookie under a no draft system than they do under a draft system while having Gobert/Hayward on the team. The fear of the big markets is way overplayed. Yes it will help them, but it would really help the Jazz also.
But thank you for the more thought out response than what others have said.
Also, I think there could be some kind of restrictions on this. Like only being able to offer so much $$$ to rookies if you are over the salary cap. Restricting how many rookies you can sign in a given year (like now each team gets 2 picks for a total of 60 picks, keep that but now it's 2 player signing vouchers that be traded. After the rookie signing period any player who doesnt get signed can only be signed for the rookie minimum.) Something like that.
