Serious question: why don't you increase the size of text on your OS as a whole? Or browser default zoom at a minimum? If you're having to bump up the size individually on most sites, it seems like the problem is that your computer is misconfigured, no?

Regardless, the point is that it's important for body text sizes to be roughly consistent across sites, so that you can find the zoom level that's right for you and stick with it, rather than have to adjust it for each new site.