Over the years steps have been taken to make suicide more difficult than it used to be. OTC drugs such as paracetamol are only available in small quantities. Catalytic converters and diesel engines produce much less CO. Natural gas has replaced town gas. Etc, etc. All this means that the railway is now one of the most accessible means of self-destruction. Clearly more can be done to make the system more secure - look how rare suicides are on HS1 - but at a considerable cost.
I'm afraid emergency services are currently dealing with an incident in the Dagenham area on HS1