suicide may be the result of a temporary depression episode and so stopping you from doing it may result in you being glad they did later
I hate that attitude.
Choosing to study philosophy instead of something vocational may be the result of compromised thinking. With time, people who obtained philosophy degrees might later feel like they wasted their time and money. Thus, we should impose our will on them - force them into another field of study - in the hopes that they will be grateful to us later on.
Also, someone's suicide can be devastating for families,
Lots of things can be devastating to families (divorce, for example) but that doesn't justify banning those activities. Freedoms aren't constrained by your family's expectations.