Is Joomla showon only for backend?

I'm changing user profile plugin in Joomla 3.3, using method described in http://ift.tt/1E2xLGx tutorial. Everything works and OK.

But I want to make some changes in profile. In this profile plugin there are two xml files, One for administrator controlling what will appear in registration and profile editing forms, and the second one for the registration (profile editing) form itself.

showon feature works good in the first xml file, but does nothing in second file.

Any ideas about reason and solution ?