These people are fighting for their lives, and are taken advantage of by an industry. It also doesn't help that plenty of antipsychotics are crucial for people to take, but that's because those are drugs that actually make it difficult to think for people whose thoughts get out of control. They don't claim to be eradicating the chemicals or deficiencies of chemicals that cause all psychosis.
The tactic of pharmaceutical companies creating patients' groups to get sufferers together and lobby "on their behalf" has been going on since the 80s. It's bulletproof, and impossible to attack. In the case of antidepressants, they've also guided them into defending these drugs as a class, rather than on an individual basis.
Funded patients' groups also played a huge part in the prescription opiate epidemic; it doesn't matter how much science says that long-term opiates aren't helping chronic pain, you have to be heartless to dismiss someone with a known painful condition or injury when they're pleading for opiates. Even though you know that people who had nothing wrong with them before going on opiates would plead just as intensely.
On another note, there is one thing you are absolutely incorrect about: antipsychotics are not ineffective managing many mental health disorders. Large clinical trials are done before these drugs are even approved for the sole purpose of proving they are better than no treatment.