But we don't need to run an experiment to know that giving 6000 people regular income will make them generally better off; that's obvious, especially in the context of a developing country.

We need to run an experiment to identify whether redistributing tax money to everybody equally and unconditionally results in better outcomes than various other existing or proposed systems of needs-based handouts, which is a completely different scenario, not least because for a significant proportion of people in the experiment this is going to represent a reduction in their current incomes or other benefits.