Just under 40% of the Obama stimulus package was devoted to tax cuts. The bill had $237 billion in tax cuts.
That's not a useful tax cut.
If I tell you that next month, I'm going to cut your rent by half, for just that month.... is that going to drastically change your budget? No, because you know the following month, your rent is right back to where it was before.
That's not to say it didn't help in that single month, but it was a temporary and fleeting benefit. There was no sustained consistent boost to the economy.
It's the same as cash for clunkers. That program didn't benefit the economy, or the auto industry specifically. When the program was announced, people who were already planning to buy, delayed their purchases, or moved up their time frame on purchases, in order to use the program. But if you average it out sales during the program, to the slump before the program started, and the crash after it ended, the over all effect was nearly zero.
It was an extremely temporary, and limited effect. Nothing permanent or sustaining.
Same with the tax cuts. These cuts were of short duration, and employers knew that. No employer is going to hire someone with money from a tax cut, that isn't going to be there the following year.
No more than you would run out and buy a new car, because you got 50% off your rent this month, knowing next month your rent goes right back up, and you end up losing the car, and getting sued for the default.