Ugh. I've gotten litter and morning glory, but never that. An assortment of different people doing tree work, wonder how many of the ones cultivating a professional image crap in the back of their trucks.

I usually get plastic pop bottles, broken rakes, and once a chainsaw! They came back when I called and got it.
I used to get stable cleanings from an equestrian center with hyperdermic needles in it. I assumed they were for the horses.
Sometimes I get Poplar or Willow chips and they tend to sprout a bit, but not to the point of being much trouble.

When the crew rakes up at the end of the job they can sometimes rake up weed seeds. That usually goes in last, and when dumped is buried and the bottom of the pile. By the time I get to the bottom, they're cooked.

bboy...

Look at it this way...

How many contracting services work at homes without restrooms?

Lawn guys are "in and out" - a quick mow and they can leave to find a restroom at some gas station. Plumbers, etc., are in the house in most cases, either with a key, or scheduled to be there with owners home.

Other contractors are there for a few days and rent Porta-Potties...

But tree guys are on site, often for hours, and half the time, homewowners are not there. The equipment is too big to pack up and roll to a gas station every time a worker has to pinch a loaf.

My guess, is that the upper end of the price range guys leave during breaks, and the budget services need to stay on site and use their trucks.

In my case, I don't use a chipper, although some of my pruning projects are extensive.

But I make sure that anyone working for me has transportation, and expect them to report to the work site in their car so they can leave at their leisure.