Yes, many lightweight boutique wheels cannot handle 140 psi. However, I've never heard that as a excuse for limiting tire ratings. For example, the popular Vred TriComp is rated for 145 psi:
http://www.biketiresdirect.com/produ...il.asp?p=VR4FO
Unless you are riding on a polished wood track, I do not see any reason for using 145 psi.