> When the `ping` attribute is present, user agents should clearly indicate to the user that following the hyperlink will also cause secondary requests to be sent in the background, possibly including listing the actual target URLs.
> For example, a visual user agent could include the hostnames of the target ping URLs along with the hyperlink's actual URL in a status bar or tooltip.
Does any browser supporting pings actually do that??
Also the "Note" in that section provides a decent argument for supporting `ping`. Basically, users will have their clicks tracked anyway, but the `ping` attribute provides more transparency and a better user experience. Though the transparency part is debatable given browser implementations.