There are a variety of attempts to explain the difference.

I'm not sure how true any of these are but:

1) women self harm more frequenty than men, which means it's more likely that they get early intervention and help.

2) women communicate better than men meaning they get constant low level support and easier path into treatment

3) men use methods that are more lethal and less survivable.

4) stigma, discrimination, lack of understanding, etc. many people have no idea what mental health treatment involves.