There are two topics in this question: Universal Basic Income (UBI) and Hive Stake Based Income (SBI). First, I'll cover the general idea of UBI, then I'll cover the specific implementation that SBI provides.
The most common version of UBI is a system where everyone will get enough money to stay above the poverty line. Everyone would get this money, regardless of your situation, income or social status. For context, I'm from the Netherlands, a welfare state. We already give a lot of money to the poor, theoretically enough to live from.
There are many differences between UBI and our welfare system though. To start, UBI is a lot easier to implement. All our welfare payments have complex requirements that should be met, while UBI is just a single price paid to everyone. This is also where a con starts to show up. UBI is not flexible at all. It's a no-strings-attached payment. But it does solve a couple of problems we're currently facing, mainly that it doesn't fall away when you start working from unemployment. (If you want to know more, I suggest this kurzgesagt video)
The team of the Hive SBI system claim to have created an implementation of basic income on Steem and Hive. It is not, however, a universal income. Only the people that can afford the tokens will get profit, and the more tokens you have, the more money you'll get. That means that it doesn't solve any of the problems UBI is designed to solve, and it's basically just vote selling. With one big difference.
The sole purpose of most vote selling bots is to play the rewards pool and abuse inflation, nothing else. SBI is slightly different. To get your investment back, you have to spend a significant time on the blockchain, and you have to create content regularly. Many others in this comment section have mentioned it already. It provides an incentive to stay on the platform. SBI encourages you to check back and write a post after a period of inactivity, because you'll have an upvote waiting for you.
While I do think that SBI is a lot better than most other (now dead) vote buying services, I still prefer to see manual curation. That was the original idea of the blockchain, and that's the only way forward for the blockchain.