TOOOO easy to sell your tickets to whoever, electronically. And before REGIONAL fans even get a shot at tickets, "Brokers" already have them. These Brokers know EXACTLY who is buying them. You can probably add Travel Agencies to the issue also. I bring it up a lot but when I was in the Coliseum for the Saints game in 2019, I saw WAAAAY too many perfect blocks...some rather large...of Saints fans that were in PRIME seats. VERY prime!! That I know are not sold via calling the Rams ticket office a week or two before the game. NFL teams themselves could investigate but they could not care less if their respective stadiums were 90% other fans. It's Butts in seats.
Niners came to Jacksonville about 20-22 years ago. WAY before Ticketmaster wormed their way in and WAAAAY before electronic tickets. Niners still had Steve Young. They were still pretty decent. There could not have been more than 1500-2000 Niners fans.