Self-report tests are useful because they have good:

Self report test are useful because they have good in reliability in which results that are obtain are reliable and are considered valid. Another thing which made them useful and be of advantage is that they don't cost too much and are considered to be inexpensive than other psychological tests.

Self-report tests are useful because they have good first and foremost, they are from the person himself who uses self introspection in examining his body systems. It is therefore an effective examination to further know a person's certain conditions given with his/her honesty in dealing with it.

It should be illegal