If you look at the standard Championships Bid Application furnished by USATF you will find the following gems:
Successful Bidder may only contract with sponsors, suppliers, or vendors approved by USATF as it relates to the Championships.
USATF Sponsors shall be given first choice on prime locations in the exposition area, free-of-charge.
USATF reserves the right to name additional sponsors or suppliers and augment the list of protected categories at any time.
Bidder acknowledges that USATF owns all revenue sources, including all commercial rights to the Championships, including media, marketing and licensing rights. USATF may negotiate in good faith with Bidder to transfer certain mutually agreed upon rights to Bidder.
To the extent that USATF approves and Bidder is able to secure additional sponsor revenue, USATF shall be entitled to receive a percentage of the gross amount from said revenue.
Bidder shall provide a hospitality area, beverages, and amenities for the use, comfort and entertainment of .. . . USATF Sponsors.
Bidder understands that it does not have the right to contract with any sponsor, supplier, or vendor without the express written consent of USATF.
Basically the USATF gets the lion's share of sponsorship money. Nike, Toyota, Hershey, Gatorade and Comcast/Xfinity are all official sponsors so companies like New Balance, Ford, Red Bull etc. are vetoed. If you do manage to get, say, an airline to sponsor the event, well, USATF shall be entitled to receive a percentage of the gross amount from said revenue. Note gross amount, not net, so the cost of that free expo space, hospitality etc. comes out of your cut, not theirs.
Finally, you have to use sponsor equipment. So even if your city has a fleet of Ford vehicles you can't use them, lease some Toyota's instead.
It's no surprise that the big incentive dangled by the USATF (and Olympics, World Cup, Formula One) is $millions of tourist revenue. The event itself will loose money but imagine all those tourists throwing $100 bills around like confetti. The tax payers will love the city for investing their money in the event.