In Switzerland, filing for divorce, whether jointly or through one spouse's claim, generally does not require a reason for the marriage's failure. A joint application need only state that both want divorce. A claim must establish two years of separation or unreasonableness. Reliance on unreasonableness is the sole exception to the absence of a duty to give reasons: it must explain why waiting two years is unreasonable. This often, but not always, coincides with the reason for wanting to end the marriage.
In short: Unless you base a divorce claim on unreasonableness, but instead file jointly or after two years of separation, you need not explain why you want to divorce