During the 18th century,stones like this dotted the mail routes of Yorkshire. The primary mode of transportation during these times were horses or horsedrawn carriages. These mounting blocks let riders hop up onto their steeds with relative ease.
It's not surprising to find these stones located outside a pub, considering drivers and riders were often in need of sustenance, and liquid or otherwise. It's also not unusual to find steps carved into the stones to aid with clambering onto an unstable target.
Source: atlasobscura.com