OK, maybe there's a reason but I don't know it. The libtool package that comes with redhat simply dumps a bunch of sources in your share directory, but no compiled libraries. As a result, the build process for an Open Source project I'm helping with (http://www.quasimodo.org) is butt-ugly. Why is there no libltdl.* in the libtool rpm? (jfm3)
Adding the library to libtool would necessitate changing libtool from a noarch to a per-arch package. So far, there is no Red Hat package that needs the functionality supplied by the libtool libraries. Can you supply some more details regarding why the libtool libraries have to be included? Meanwhile, it's pretty trivial to make an arch-specific libtool package including the libraries if that simplifies your project.
Fixed in libtool-1.3.3-2 in Raw Hide.