Tips at the drive through?

Inappropriate. Servers in restaurants are paid a wage that anticipates receiving tips for good service. Fast food workers receive a wage that does not anticipate tips and have little opportunity to provide exceptional service.

In the US it seems that most people think they get a tip just for showing up at work. I am happy to tip if someone does their job to my satisfaction. If they go above and beyond the norm, without being smarmy, I will tip higher. if you tip everyone there is no incentive to improve.

There is no requirement for you to tip a fast food worker; they are already paid wages for their efforts. However; it is understood that the wages for a fast-food employee are very low, as it is a no-skill job. some may find it acceptable to give a little extra.

I, having worked in the industry for 4 years in my teens, never tip fast food workers.

Where dont they have a tip jar in usa? Doesnt obviously mean u must put money in all of them

Anywhere you have college or high school students working for minimum wage or less, it's appropriate for them to ask; you aren't obligated.