So? If they wanted to die, that's what they wanted. Do we have to forcibly be required to live in a mental institution, pumped with drugs, for the benefit of others if we don't want to be here anymore?
People who are suicidal with a plan are not generally thinking clearly and are happy that they received care once they've been treated. We take people who are acutely intoxicated or unconscious to the hospital all the time and have no qualms about that.
Regarding being "pumped with drugs", I can only speak from experience rotating for 6 weeks at two different psych hospitals, but the only people who I saw forced to take medication were acutely psychotic, manic, or incredibly agitated. The schizophrenics that are picked up and brought to psychiatric hospitals generally are so psychotic that they would not be able to care for themselves - risk of harm to themselves. Same thing with acutely manic bipolar patients.
As if preference on this is always treatable. For example, what kind of treatment do you give a person who wants to die because they have no support network and had a stroke which rendered them disabled and homeless? What realistic treatment is going to give them hope? A bed in a state funded nursing home surrounded for the rest of their days by untrained, uncaring people who are just there for the low wage paycheck?