just reread the post and noticed your question...

why do they need a mental evaluation when i go to the pdoc every 2-3 months ?
(my mental state has not improved)

getting a mental evaluation is different than going to a pdoc every 2-3 months.

a person sees a psychiatrist for therapy and medications. a mental evaluation is a test that pychiatrists administer. the test has many components, theres computerized tests where your psychiatrist gives you a test with lots of quesitons on it and you choose which answer is correct for how you are feeling and what you feel your problems are, theres also verbal tests where the psychiatrist will ask you questions or to look at pictures, theres tests like you did in school math and logic, geography,

all the tests are looking for what your mental disorders are, what your mental maturity is, what your accademic understanding level is, what your coping skills are, how you think, what you believe, what emotions you are able to show, what stressors are in your life, along with other questions and what your functioning level is, and what treatment options are best for your problem areas the testing procedures and tests discovered about you.

getting out of this by claiming hardship...sometimes it works but most times it actually works against you because they usually ask you to go through these tests when they need more information. and most times its the more information that gets someone to stay qualified for their SSI.

some locations when you claim hardship/problems with going to these appointments arrangements are made so that the testing can be done in the persons own home for example some people with agoraphobia qualify for treatment providers to make home assessments.