This has been sold as a means of distributing their token. Bitcoin used mining 9and still does) as the initial means to distribute the token. Ethereum used the presale coupled with mining. Stellar claim they are issuing tokens to individuals who hold bitcoin as they are proven crypto users etc. I thought of dumping mine (and did with some) but after looking into Lumens, they seem to be one of the better alts so I am hanging onto a few. Maybe that was partly the idea!