I don’t fully agree with what you say. More specifically, the B and I elements do not have semantic value—they are purely presentational, and they’re meant to be that way, because people indeed abuse the STRONG and EM elements otherwise.
I do believe that presentational elements such as B and I are useful. Many people believe semantic markup itself is a goal, but it really isn’t. Semantic markup is simply a means of achieving something higher, e.g. making a web site easy to maintain.
(I’ve written about this before on my own blog.)