I think I caught it from the spec and from reading about accessibility in techy media some time ago (A List Apart comes to mind). I got the idea into my head that the W3C specs defined "doing it right" in part as "accessible," and equated or at least correlated "machine-indexable and searchable" with "accessible" and "logically structured" with "accessible" and the rest was history.

That, and I was slow in getting a big-bandwidth connection, so alt tags and avoiding trendy animated junk made my life better for quite a while, too.