I beg to differ.
OK, the New Age pseudo Tai Chi that's taught "for health" isn't for fighting, but at its core it's a martial art: the man who first brought it to wide attention, Yang Lu Chan, was the chief combat instructor of the Chinese Manchu Imperial Guard. A significant number of teachers (esp. those from lineages like that of
Cheng Tin Hung) still teach it as an effective fighting art. Have a look
here and
here for some more details.