One thing the software industry has been very good at doing is driving the sales of hardware, by requiring more and more resources --- only to do much of the same things as before, maybe with some improvement in specific areas. Many users have no need for the latest hardware nor software, yet they're constantly encouraged to upgrade for security, "new features" they'll never use, etc. (I'll admit that some of these, like security, could be valid concerns.) Upgrading to newer software with higher resource consumption, they wonder "why is it so slow?", and that eventually leads to perfectly fine hardware going to waste. In particular, the extremely fast upgrade cycles of browsers makes their contribution to this gross waste a bigger part than a lot of other software.
> The people who use this unmaintained software are inherently less safe.
A lot of exploits today won't even run on older systems. Older browsers also having less features is also a reduction in attack area - e.g. if there was something vulnerable in HTML5 video or CSS3 animation, a browser that didn't support those features would be inherently immune.