This should also apply to stadiums where, for reasons I cannot even fathom, small cities throw billions into a building that they don't own, that has an astonishingly short life-span, and for which they derive very little in the way of actual benefits.
Unfortunately, many corporate tax breaks are created to compete with the municipality next door for economic activity that would occur in any case. The key point is that even if all municipalities banded together and agreed not to TIF, then the economic activity would still occur.
Concretely, here's a list tallying the value of Wal-Mart TIFs: http://www.walmartsubsidywatch.org/state_tallies.html
Now, here's the key question: would Wal-Mart (or a competitor) have built all those stores and distribution centers without TIFs? I.e., is Wal-Mart profitable without tax subsidies?
The answer is obviously yes: those stores would still be enormously profitable, so Wal-Mart would still build them. Which means these tax breaks are not creating new value or spurring economic activity that would otherwise not occur! These TIFs are simply a wealth transfer from local taxpayers to Wal-Mart executives and shareholders, orchestrated by playing municipalities off of one another.
Hundreds of millions of Americans pay extra taxes and/or receive inferior services because municipalities won't cooperate in a game of prisoner's dilemma. Great for the Waltons, though.
TL;DR: because allowing municipalities to compete using TIFs results in wealth transfers from local communities to large corporations without creating new economic activity that wouldn't have occured anyways.
People see salaries of FAANG engineers and think that those companies pay well in gneeral, and furthermore that the tech industry pays well in general.
I've seen this first-hand: people were super excited about an Amazon distribution center being built in a town I used to live in. The thought process goes something like: "Amazon says they'll be hiring hundreds of people and that they will train people on the job. Also, Amazon engineers make 100k. Therefore Amazon will hire me, train me, and I'll be making 100k!"
I think the ship has now sailed on Amazon; people today realize that an HQ full of engineers is different in kind from a distribution center.
But the cycle continues with other low-skill and medium-skill "tech" jobs. For a particularly striking example, see some of the rhetoric around the Foxconn plant in Wisconsin...