> Unfortunately SEO ruins great, witty and brief marketing texts.

SEO content marketing is basically a descendent of direct marketing -- the stuff you used to get in the mail, in two-page spreads in Reader's Digest and so forth.

Direct marketers have known for a very long time that long-form copy sells better. They had the numbers to prove it long before "analytics" was a common idea -- the very term A/B testing refers to the "A" and "B" sides of a newspaper print roller being able to print two versions of an advertisement.

Source: Tested Advertising Methods by Caples. A fascinating, if depressing, read.