The majority of people initially contact the floor with the lateral side of their heel, which is why the posterolateral aspect of your shoe probably has the most wear and tear. This initial contact will create a slight pronation moment leading to pronation in midstance.
Pronation is a NORMAL motion occurring just below the ankle at the subtalor joint, giving an inward rolling motion decreasing the arch of the foot leading to helping absorb shock during walking/running.
When either the shoe heel or lateral flare is excessive, there is an INCREASED the pronation torque. This can lead to Excessive pronation which has a variety of different problems it is associated with including: stress the plantar fascia & inverters as well as causing Hallux Valgus #notpretty. These impairments can also work their way up the chain producing potential knee/hip/back pain.
Something to consider if you are a runner, walk a lot throughout the day, or just want to avoid being apart of the #pronationNation