Not being able to access a website won't stop someone from having suicidal feelings. But every barrier placed between a suicidal person and their ability to kill themselves makes it less likely that they die, and more likely that they seek help. Remember when you used to be able to buy a nice jar of 50 paracetamol? Someone in the home office did some maths and calculated that selling paracetomol in boxes of no more than 16, individually wrapped to make them harder to get at all at once, would save a worthwhile number of lives each year. Even a suicidal person has inhibitions against going through with the act; websites that aid and abet suicide are one of the things that lower those inhibitions.