Why? Required? Well, these questions go back to the old days. It used to be thought that redirects were bad, and we should avoid them, trying as hard as we can to replace them with the precise name. Then it was discovered that Google found things easier through redirects, and they provided a way for us refine Google's search semantics quite a bit. So it helps people find what they want, and avoids the problems of having to be too precise about linkages. Its more of a wiki way to do it. Not to mention that this type of linkage comes from our disambig policy, to use disambig pages liberally, but always be hierarchical according to common sense. More recently it was discovered that tools to "fix" redirects (like the one in WP:POP) are hugely taxing on the server, so that ended the last of the purists crying about link precision. The funny thing is that link precision is actually a hindance to semantic searching. So, over the years the idea has been to make WP redirects function as a part of the semantic web. That's an explanation in a nutshell. -|vertigo