It isn't limited to Amazon, and it isn't a side-effect of the pandemic. I work for UPS and even before the pandemic most drivers used a bottle or cup on a regular basis, especially if you're in a rural area. In denser areas you can use Port-a-Johns at construction sites or restrooms at businesses. Your commercial customers will likely allow you to use their restroom even if it is closed to the public. I've never heard of someone defecating in the vehicle. Leaving your bottles in the vehicle is frowned upon, but it happens.