You are right. Plastic bags altogether should be banned ideally. It was tried in Pune with limited success. BUT habits die hard! Plastic bags are too convenient to be banned so general public themselves do not uspport these initiatives whole-heartedly.
Coming to your next question about thickness. My limited knowledge tells me that a 40Micron bag can be recycled whereas any thickness below this magical figure means recycling is not possible.
Also, what you call as disadvantage, is actually an advantage in disguise since the extra cost makes people think twice and pushes them to bring their own bags for shopping! This helps reduction in usage of new bags.
Regards,
Nitin
Nitin Phansalkar
Owner - SMEfocus Solutions
Coordinator - DESERTEC-India