I think part of the problem is that we don’t really remember what things were like before these decisions became law. In the old days, police would beat people during questioning, never inform them of their right to be represented, deprive them of sleep for days, arrest family members to force confessions, and the list goes on.
The courts came up with these rules to reign in the police. The thinking is that if the police know that criminals can walk free if the police screw up, then perhaps the police will be more careful. Also, the thinking is that it’s better to let the guilty go free than to imprison the innocent.