Why do search engines penalize websites?

The purpose of a search engine is to provide relevant information to their users. The engines are constantly battling spammers to keep their results relevant and spam-free. It is similar to a game cops and robbers. The robbers (spammers) devise new techniques, and a bunch of them jump on board and make out like bandits for a while. Sooner, or later, however, the cops (search engines) catch on and the bandits are stuck behind steel bars awaiting parole (reinstatement). Those that abide by the rules, and don’t test the limits until they are established make out the best in the end. Stick with proven techniques that work, and you will not be banned.