> Why not do the obvious, which is to give every adult some free money each month?

The federal reserve isn't equipped to do this; the federal government would need to do it (as it has before using the IRS to distribute stimulus checks). The federal reserve is equipped to buy up as many bonds as necessary to put a floor under assets.

EDIT: Could the federal reserve assume an aggressive policy posture and expand out of its swim lane in creative ways [1]? Sure, but it hasn't shown the initiative to do that.

[1] https://www.marketwatch.com/story/fed-should-forget-about-it... (Federal Reserve should give everyone checking accounts, new study says)