I hear you! Entire forests have been cleared in order to fill your mailbox. It's actually (and sadly) cheaper for them to keep sending things than to hire enough staff to process the changes. And believe it or not, not everyone is on line and people still like to flip through the pages, which results in impulse buying.
And yeah, they sell mailing lists to other companies, whether or not the catalog companies are owned by the same umbrella organization. And others use centralized mailing services and are not sending out their own catalogs at all, so one big mail house handles many companies (and mailing lists).
We have 2 home businesses so we get double copies of everything including mass mailings, credit card offers, even phone books. We've lived here for 27 years, and I still get mail for the previous owner from NYU - donation requests, those alumni trip brochures, etc. I've written to them several times, suggesting that anyone who graduated some 40 years ago and who hasn't sent them a dime or updated his address info in at least 27 years is probably not a good candidate for their mailings. They don't care. I just recycle it all.
This won't help you with catalogs, but if you get a lot from charities, it may work. My mother gives to certain favorite charities every year. She makes a list in January & February, sends in her donation, and includes a note that, if they spend her money sending her more requests and mailings all year long instead of giving it to the intended purpose (veterans, cancer research, etc.), then she is crossing them off her list for next year. It works, most of the time, assuming it's a reputable charity.
Can't write any more - the mail just arrived so I have to go recycle catalogs!