Why is the Notion of Person also Descriptively Problematic?

Informally and on occasions formally, the notion of
person seems to be indispensable in many walks of life. In
philosophical debates, though, the notion oftentimes
appears to play a subordinate role. Other notions--subject,
self, individual, human being, or characteristic marks of
persons: mind, consciousness, rationality, (individual or
cultural) identity, autonomy, authenticity, responsibility--
occupy center stage. There are exceptions: there is the
venerable problem of personal identity through time; in
certain ethical issues, e.g., in bioethics or political
philosophy, conceptions of person figure explicitly; and
there are some treatises of the "concept of person" itself.
Yet, even here one can hear warnings, e.g., that the
concept is fraught with dilemmas and should be avoided in
bioethical debates (Birnbacher 1997), or warnings
concerning the "vagueness" (Wils 1997, 37) or the
"contemporary crisis" of the concept (Kobusch 1997,
263ff.).