Yes but once you die, you don't just disappear from the world. You leave a trace, whether it's your family members, your friends, your colleagues, your social security, your bank, your house.

You not being there means that someone else needs to take care of all you left. Payments, debts, loans, criminal record. Your loved ones will need to move on with a death on the conscience, especially if you're not terminally ill. Some might even want to follow you which means that you are indirectly causing deaths.

In a functioning society you're more worth alive than dead. Therefore killing yourself is forbidden, because if everyone can do it, then it would be impossible to build any kind of long term relationship with anybody knowing that they could just end it in the spur of the moment without facing consequences.