That's probably because about the only browser to actually support it is Google Chrome. Oh and Safari (sort of), and the time it is likely to "save" could be measured in microseconds, unless your users are in some [insert name of deity] forsaken glory hole in the Australian outback using a 33k modem of course.
And the ONLY
people who need to even CARE about it are republishing somebody else content, if your content is ON YOUR SITE
why do you need to pre-resolve DNS lookups?
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A foolish consistency is the hobgoblin of little minds
Thought for today:- Is SEO the only industry where all the cowboys are Indians?