People are not going to spend $ to mail heavy batts thru the mail.
Besides, it's unnecessary. EVERY municipality has a hazmat program where you can turn in batteries.
Some communities have a drive-thru once or twice a year where you bring your bathroom cleaners, paints, batteries, etc. by the carload. Others allow you to drop off.
Just call your local disposal company. I have to haul my own trash to a disposal site every week (we don't have trash pickup as far out as I live in the woods) so I have a box where I separate hazardous stuff and I hand that over separately.
After studying hazmat articles I was amazed at how so many household cleaning and bathroom cleaning materials are considered hazmat. i.e. not safe for regular disposal according to all the disposal companies.
Which of course, made me stop using them in my home. I wonder why people with young children spray that stufff around all over the place. Something to think about! Even the containers are considered hazmat.
Just because it's sold OTC doesn't mean it's safe or non-carcinogenic.