If we have a program, e.g. a custom text-filter, that can strip html tags and other markup (formatting) from original text (content), then why do we need a brow

If we have a program, e.g. a custom text-filter, that can strip html tags and other markup (formatting) from original text (content), then why do we need a browser? The very early ideology of HTML was to describe structure and content fairly minimally so that browsers could display it in whatever manner was right for the user. But it turned out that content producers had more influence with browser makers than did content users (who after all don't pay anyone but the ISP). And they want to have control over the user's screen, speaker and (ultimately) brain. Hence pixel-perfect formatting, advanced CSS and of course JavaScript. But that has sort-of changed for Mozilla. Their competitors have all the close relationships with content producers, so they are trying to become friends with users again. And thus their incentives have shifted to trying to recover the original virtues of the web out of the current set of technologies. It's a tricky thing to do, and I wish them luck.