How does this result in a net-increase in plastic waste? Were you somehow getting the exact number of bags you needed to use as bin liners, and now you buy extra?

I usually had no more than 3-4 disposable plastic bags saved up as bin liners.

Now I have to buy bin liners, as well as the occasional reusable plastic bag. The reusable plastic bag has 4x the plastic content of the disposable ones.

What happened to the other disposable plastic bags you took home? Presumably your garbage output was less than your grocery input?

And yes, having to buy a new reusable bag if you forgot yours is frustrating. Which makes it memorable, and less likely to happen again - though that may be more of a personal thing.

If you have a lot of extra reusable plastic bags, perhaps you could push your local grocery store to put in a "take a bag/leave a bag" box? To ensure they get put to good use

Some of these eco-rules result in inconveniencing your life and increasing your costs with at most a zero change of the overall plastics use.