Because (it feels) like it's not possible to properly debate the subject in public. As a little/normal person the answer is always the same: "But but what if it was your mother/girlfriend/daughter that died in the attack?!". These are the same people that probably have been into contact with someone who has directly dealt with the consequences of police corruption, yet won't ever support "making the police's job harder".

Once an attack "gets through", which will always happen eventually, anyone that didn't support the PersonalRights-Devouring Anti-Terrorist Bill will get crucified by the press and their opponents.

Most people don't appear to care about numbers, or facts or evidence. They only seem to care about pushing their ideology (normally authoritarianism) that "makes them feel safe", rights and freedoms be damned (which is why I can never take the US's obsession with "rights and freedoms" seriously).