Why do they keep sending me this garbage?

Spammers continually send email with different subjects and offers in order to entice users to buy their products. Many of these products are; fakes and knock-offs or potentially dangerous to the purchaser. Due to the low cost of sending spam, even with the extremely low response rate, spammers can make a significant profit fairly easily. The more emails a spammer can send, the greater his profit while the cost remains nearly zero.

Spammers rarely honor opt-out requests. It's work for them to process opt-outs, sending less spam doesn't cost them any less, and who knows, you might be one of the suckers who responds next time.