Manual:$wgDisableCounters

Details
$wgDisableCounters  determines whether or not to update the number of times a page has been viewed. If $wgDisableCounters is set to false, each page will have a counter in its footer saying: "This page has been accessed X times"

This setting also determines whether Special:Popularpages is available.

This variable is initialized in. The initial value is. To override the default value, add the line  to the file

The value of the counter is updated in  in the function. The variable  is also referred to in other script files.

Alternatives
If performance problems due to high hit counts updating the site_stats table is a concern, a less dramatic alternative to disabling them may be to tweak $wgHitcounterUpdateFreq.