Why do some graduate work records not include an abstract?

Why do some graduate work records not include an abstract?

ProQuest began including abstracts for doctoral dissertations in 1980, and for master''s theses in 1988.  Any graduate works published prior to those dates are unlikely to have an abstract included in the citation record, though some do.  Almost all dissertations published after 1980, and almost all master''s theses published after 1988, will have an abstract in the citation record.  If you discover a record published after those dates that you think should have an abstract included with it but doesn't, please contact Technical Support and we will investigate.