Kenneth G. Wilson (1923). The Columbia Guide to Standard American English. 1993.
want (v.)
has three main meaning clusters: to wish or desire, as in Do you want a second helping? (see DESIRE); to lack, as in This deck of cards wants a nine of clubs; and ought (to) or should, as in You want to be careful on icy steps. The first two uses are unquestionably Standard; the ought (to) meaning is usually limited to conversation and the Informal and Semiformal writing that imitates it.