Vlad,
Just to clarify CVS support in Eclipse is developed by the Eclipse team (www.eclipse.org) and doesn’t tie into the MyEclipse product.
As far as why Eclipse doesn’t support it, I’m not sure why. Maybe there is something on the newsgroups, FAQ or listserves about it. A quick search of bugzilla shows that there are already requests for it, please add your comments/votes for these bugs to see it get implemented in eclipse:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=37414
https://bugs.eclipse.org/bugs/show_bug.cgi?id=41097