Here we have competency based training so performance in various units has to be scored 1 (CPL standard) to 4 (been shown it and can just about do it) plus comments which the student reads and signs as a fair account of the flight.
I remind my instructors that in worst case the records may be used as evidence in a court (as per Life's a Beech's post) should the unthinkable happen. In any case I should be able to pick up the file and get an overall picture of their (and the instructor's) progress.
As for tardy record keeping, with casual instructors I withold wages unless the records are complete, as IMHO the job is not finished until the paperwork is done. They are told this from the start so no excuses.
Am appalled that some instructors come out of training able to do nice landings from the RH seat and draw pretty pictures on a whiteboard, but have no idea of thier legal responsibilities. Some have never even seen the syllabus.