Why should I spend all my time learning SEO when every time I do a search I find the 1st 3-4 entries to be paid ads? Think of it! You could be right up there with Forbes and Hubspot!
Yes, yes ads cost money. But I've spend a great deal of time and energy and have paid for the occasional SEO course.
And the SEO ranking methods can be quite formidable if you are starting from scratch. If you don't take a sizable risk in paying for links you can spend eons contacting possible webmaster who will take a link.
Of course, there are those who will say, 'why don't you do both?' Which is what will probably be doing. Still, the question lingers...