Haven't truckers always done this? Seems like a shipping industry problem and a problem with the complete lack of public toilets in America.
It is true that a lot of public toilets have been closed for the past year but these complaints go back to long before that happened.
I don't know where you live, but where is there a bathroom to stop at? The US isn't filled with public restrooms everywhere along driver's routes with convenient parking right outside.
To use a public restroom could easily mean a 10 minute drive, 5 minutes to find parking and walk to the bathroom, a 10 minute wait in line when it's separate bathrooms like a Starbucks, and another 10 minute drive back to resume your route, like 35 minutes total. Yikes.
I mean sometimes you might get lucky where there's a gas station right along your route and you can pop in, but most delivery routes snake through residential neighborhoods. There aren't any public bathrooms to be found anywhere.
Where I've lived in several smallish cities in the Midwest it is generally not hard to find bathrooms. I've had jobs that involved driving a van between customers' houses and never had trouble finding one. They're not in the residential neighborhoods but the routes would always go reasonably close to at least a few gas stations a day.
But even here where we do have bathrooms fairly readily available the drivers still pee in their vans. I know because I used to work in one of the local Amazon warehouses and we would find bags the drivers had returned with pee in them.
I'm not defending Amazon's general financial screw-turning, but I think the "peeing in bottles" has only become a meme because the idea seems gross to everyone who hasn't spent a long time alone in vehicles.
Note: I would not want to be forced to do that by my employer.
You can find bottles filled with yellow liquid all along major highways.