Because they're taking income from the rich and giving it to the poor. Poor people are more likely to spend. If instead they took the money and gave it to rich

Because they're taking income from the rich and giving it to the poor. Poor people are more likely to spend. If instead they took the money and gave it to rich tax payers (which I imagine would be deeply unpopular), then this would likely reduce inflation as rich people typically would save it, and thus remove it from the consumer spending category.