The Dallas area is a major tech hub. It’s just an older hub of major enterprisey type companies with major tech divisions there like Texas Instruments, AT&T, Bank of America, defense contractors like Lockheed, etc.
Office Space took place there before the dotcom bust.
Less enterprisey, but John Carmack and id Software also started there.
I lived and worked in Atlanta from 1996-2020. Those aren’t anymore tech companies than Delta, Home Depot or Coke by modern definitions. In all of the companies you named, software development is a cost center, not a profit center - follow the money. Who gets paid the most as a group at those companies? Those are enterprise companies.
Office Space took place there before the dotcom bust.
Less enterprisey, but John Carmack and id Software also started there.