This is intentional, I didn't want to force people to install modules
they weren't going to use, so I only put in prerequisites for things you
absolutely do need. WWW::Mechanize is only needed if you are using the
WWW::Google::SiteMap::Robot module to build sitemaps, if you are
constructing them yourself you don't need that module, and therefore
don't need WWW::Mechanize. DateTime is not required, but the
WWW::Google::SiteMap::URL module will accept DateTime objects for
setting date elements. There is currently a bug that makes DateTime
required, which is probably why you ran into problems, but it will be
fixed in 1.05 which will be released soon.