WireMin markets itself as a decentralized service. The question was “why use this”, so I mentioned the pros of using decentralized services. I did not ignore the question. WireMin should not be used. Other (truly) decentralized protocols like Matrix, XMPP, or anything running on ActivityPub have benefits over services owned by companies like Signal or Telegram.

However, most people are locked into a platform by their contacts, and their contacts choice of chat application. If most (or all) of your contacts are already on Signal, there’s no good reason to use anything else.