I totally agree - my philosophy is why should I pay to advertise the shop/company (although I do have Tesco Bags for Life - but they get used in Asda, Aldi and Lidl, even in Poundland!)
I have voiced my dis-satisfaction in Markies - "do you want a bag" - only to find after I left the shop that it had been added to the receipt.
Next time I was there I commented that I had not been told I would be charged for a bag and I object to pay to advertise etc. - so out came the Tesco bag
However, I wasn't charged at all twice this week in Markies!