What is the purpose of the uucico shell on HP-UX, Solaris, and possibly other Unix varieties?

I'm not a Unix admin myself, but I work with Unix servers on a regular basis and am fairly familiar with their workings. So maybe this is something obvious, but it's not something I can find an answer for and my SAs all seem equally clueless. So I'm asking you guys. On Every HP-UX and Solaris server I've worked with there has been this shell, /usr/lib/uucp/uucico which seems to come out of the box with weird file permissions and is only used by the uucp user, but it is listed in /etc/shells as a valid shell. I've tried to find a good answer online, but as far as I can tell there doesn't seem to be a good reason for uucp to have its own special shell and could just as easily work with sh or something. So I think I must be missing something. What is the purpose of this shell? Why is it there, and what does it do?