You wear your glasses all day, people see you with them on, they interact with you with them on. Like it or not, your glasses become an integral part of your presentation.
A pair of glasses that do not flatter your head size, shape, eye shape, etc, are not the right pair of glasses for you.
Did you know a person with a round head should not wear round glasses, whereas a narrow head, or someone with sharp features, is much better suited to round glasses. These are general rules of thumb, and choosing the right frame is more an art than a science. Each person has nuanced attributes about their face to make hard rules about lens choice. That being said, with basic heuristics, some taste, a great deal of experience, a professional can not just help you choose the right eyewear, but custom craft them for you as well.
When you get a suit, the tailor takes measurements, examines your build, your gait, and customizes a suit to best fit you. No one sees this as unnecessary, and yet you only wear a suit a few times a year. Why not go through that same process with a pair of glasses, something you wear all day every day.