Very easily. It is because i manufacture things, and know the prices and costs of manufacturing. You can go online and order t-shirt bags. See the prices, and compare.
A canvas bag is definitely nice. I have the same backpack i have been using to collect groceries for decades. The bags sold in stores are plastic cloth. And not as durable. Further, i have seen people throw them out because they got something spilled in them. And spills are more common then we would like.
The cheap plastic bags that i have acquired have all been used instead of buying thick plastic trash bin bags.
I believe the term to look up is "high temperature rocket stove" or a two stage rocket stove. But basically, it has a vortex burning secondary chamber where the temperatures get up to a couple thousand degrees, burning everything. Efficiencies are very high and pollution is very low.
You use a similar thing for burning garbage.
But, wouldn't you know it, the govern-cement won't let it happen.
You see, the garbage department is over here, and the power company is over there, and we can't have them intermingling.
Ah rocket stoves I'm familiar with. But it seems to me your last statement just confirmed what the original post was pointing to.
We can blame the government and the system or recognize that each of us has the power to change those systems and little bit with our choices. You prove this is with your own grocery getter. If enough people cease a practice then that practice becomes impractical, irrelevant, and unnecessary. The few holdouts that still take the bags will have no choice but to follow or else learn to juggle.
The problem is one of awareness and apathy. Changing those two things requires education obviously for the next generations and reprogramming for current ones.
Additionally as a minimalist (like hardcore as shit with literally everything I own in a backpack for the better part of a decade minimalist) I have no problem pointing out that in much of the "developed" world people use way too much shit. Television and Internet ads, pop culture, parents and friends condition people to equate their identity and value to things. This is a major flaw in the system and hurts all of us in the long run.
Our obsession with status through materialism has potentially cost us great advancements in knowledge and understanding.