Even if you have an insurable interest, moral hazard may arise - acting recklessly or other abuse, while knowing you are insured/covered. Somewhat similar to friendly fraud in retail/ecommerce.
You can get insurance without the above provisions, but it will cost a lot more. Once in a while someone manages to collect on a claim for loss of their expensive cigars after they smoke them - but this is rare and usually not worth the cost.
This may vary by country, it isn't a subject I'm particularly familiar with, but at least in the UK that isn't true - many, I think most, life insurance policies here do pay out for suicide. There's just a period of years between the start of the policy and when suicide starts to be covered, to prevent people who are planning on killing themselves from being able to take out insurance just before doing so.
if there is evidence that someone took out the policy with the intention of creating a claim then the insurer may treat it as fraud and decline it.