It isn't a secure product, but it's a crypto product something that has decent UX that isn't from a huge compromised company such as apple or google. In this space it makes it rare. It all depends on your adversary. For family members, stalkers and most employers, it's probably great.
Well it's more a social design. Google probably has a record of all of your emails, deleted or not somewhere and a court order can get those emails. Cryptocat will not. Gmail is also very integrated into most people's devices, so it's easier to get to someone's email records by getting at their computer, phone, cookies, etc.
