You miss the big picture of "the web" rather than "a dev", or "a web site". The more pages, across all devs and all websites, that build their content in a way

You miss the big picture of "the web" rather than "a dev", or "a web site". The more pages, across all devs and all websites, that build their content in a way that omits the optional tags in HTML, the fewer bytes we have that need to be pumped through data centers and routing paths on the planet. It's not so much about "if you're google" but "if we all do this": a 0.001% reduction in global byte transfers would constitute a massive saving despite looking like a tiny number.