The W3C publishes all these standards for HTML and CSS but browser vendors implement them inconsistently (or not at all). IE has its own box model, Netscape has its own quirks, and we end up writing hacks for each browser.

Is the web standards movement making actual progress or are we just yelling into the void?

It's slow but it IS working. IE6 supports more CSS than IE5 did. Mozilla is nearly fully standards-compliant. Each generation gets closer.

The Web Standards Project (WaSP) is doing important work pushing browser vendors. Jeffrey Zeldman's advocacy is making a difference even if it doesn't feel like it.

Standards matter for accessibility. If everyone wrote semantic HTML and valid CSS, screen readers would work better and the web would be usable by everyone.