Especially useful for single page applications but also if someone does not want to have piwik.php links in his page.
piwik.php redirects are currently used if a link goes to the same domain.
works only in Chrome so far I think... IMO piwik.php redirects should be disabled by default as it works for all sites and optionally users should be able to enable it in case they want it.
There's no reason to be able to enable it anymore since there is enableSendBeacon etc. The redirect is slower etc and shouldn't be needed.