Wearing down the heel lining is a common issue, especially if it’s loafers or other shoes where you tend to have a bit of heel slippage going and which you might wear barefoot as well, which increases friction. The simplest solution to this is attaching these self-adhesive shoe repair patches.
We’ve just started selling various versions of them at the company I work for, Skolyx. They can also be used to repair holes and cracks in the upper, you attach them on the inside of the shoes, however it depends on where the hole or crack is located etc on how well it works, if it flexes too much it can come loose. As always taking them to a cobbler will end up with a better result, especially for repairs of the heel lining, but it can be a good easier and cheaper solution.