As someone with presbyopia, and light myopia that first developed around the time I hit 30, who used to have excellent vision, I promise you that sooner or later you'll regret not thinking about accessibility.
For the record, the default choices for text size here on Hacker News are an example of ignoring basic accessibility.
Replying to myself to add: the suggestions to "just use the browser or OS controls" are beside the point. It's not only possible but easy to give users more control over the font size and maintain control over the layout and look of the site. Just cranking up size locally doesn't take into account design factors for text and other UI elements.
https://www.w3.org/TR/WCAG20-TECHS/G178.html
Also, pushing responsibility for dealing with poor accessibility onto the person with disability is exactly the attitude that itself perpetuates the problems.
G178: Providing controls on the Web page that allow users to incrementally change the size of all text on the page up to 200 percent: https://www.w3.org/TR/WCAG20-TECHS/G178.html
For the record, the default choices for text size here on Hacker News are an example of ignoring basic accessibility.