One purpose of a lump sum distribution such as the monthly "basic income" is to counteract the regressive nature of consumption tax.

For example, suppose we want to provide free mass transit. We then get terrible rush hour traffic and the system is overburdened. So we must charge for transit access. Even better would be charging more for rush hour than off-hours, more for long-distance, etc. But this is regressive! Relatively cheap for the wealthy for rare events, expensive for the poor who need it for everyday commuting. The solution is to provide a lump sum grant to all citizens equal to the amount a person would pay for everyday transit commuting. Thus the poor get "free" transit and the wealthy get a few bucks and the positive externalities of transit.