Shaun Juncal makes a compelling argument in Product Accessibility Shouldn’t Be an Afterthought:

But addressing accessibility early and often—if not making it an ongoing pillar of product quality—is a best practice every product team should embrace. Accessibility enables the maximum number of potential users to engage with products, increasing the total addressable market and avoiding frustrated customers from getting tripped up on accessibility shortcomings. […]

When a product doesn’t fully incorporate accessibility, the company is essentially telling a cohort of potential users that “this product isn’t for you.”

He shares some good advice on how to make accessibility efforts a natural part of the product development process.