Lister has a long history of ultra-reliable and dependable machinery. It is my guess that they preferred to follow the KISS principle (keeping it simple). Assuming normal maintenance, an oil system failure is quite rare and in most cases, such a failure would not likely be prevented by instrumentation. Lister did include as standard fare a low oil pressure shutdown feature on almost all of their long-running genset builds - at least from about the 1960's onwards. They did not commonly instrument them though. Third parties seem to have mostly followed suit on much of the equipment we commonly see in North America.
dieselgman