I think a big part of the issue is how the subtances work and how the tests work.

Are there tests that indicate past use of alcohol or just the ones I'm aware of where the measurement drops swiftly as alcohol is processed?

Same for marijuana; is there an objective(ish) test that indicates current intoxication or only the tests that show use within about a month?

Marijuana does stick around a long time, but they test for other stuff that doesn't, some benzos, heroin, etc. There's apparently something called an ETG test for alcohol consumption that can reach back a few days.

I dunno. Background checks include DUIs.

You don't get a DUI just for being drunk on the couch on the weekend, you have to also be operating a vehicle while drunk. Which is what the parent comment was talking about -- it's not regulated in the same way that pot usage is.

Every alcohol consumer has a DUI? Maybe in Wisconsin, but not in general