You seem to be making a lot of assumptions. For all you know, they build websites or applications that don't have any need to run on older browsers, or at the

You seem to be making a lot of assumptions. For all you know, they build websites or applications that don't have any need to run on older browsers, or at the very least, there are diminishing returns. There's always an opportunity cost. While you're building support for older browsers, they could be adding valuable functionality to their software. Which is more valuable depends on the situation.