What would be the point of offering paper bags, when they can instead sell you their high-margin reusable cloth bags (which are common in Canadian grocery stores)?
To provide a convenience to customers that didn't bring a reusable bag and don't want to spend a few bucks on a bag they'll never use again and has an environmental impact 1-2 orders of magnitude worse than a single use paper or plastic bag.
> and has an environmental impact 1-2 orders of magnitude worse than a single use paper or plastic bag
presumes this:
> a bag they'll never use again
...right?
Which seems strange to me, given that people will really only buy the bag if they are planning to use it multiple times.
Measuring it as if it were a single-use bag, would be a bit like measuring the environmental impact of solar panels + batteries, as if they never generated any power (and thus never displaced any grid consumption of "spiky load" coal plants et al) and only existed as a cost of initial chemical construction.