Automation changes the source of production from workers to machines. And that separates the source of production from the source of consumption.
To put it simply, robots produce wealth but does not consume it. Humans consume wealth, but (in this possible future) can no longer produce it. Robots have owners of course, but even if you ignore what happens to the majority of people, a few extremely wealthy people can not possibly make up for the consumption shortfall. Ten-thousand people with 10k each vastly outconsume (by necessity) a single person worth 100M.
So, if the entities making wealth and those using wealth become separate, you need a way to transfer wealth from one to the other. If not, you will see a slow-moving economic collapse, as lack of demand and cost-cutting automation drive each other down.
A basic income, generated from a tax on production (transaction tax, energy tax, direct tax on machinery) is one way, and has the benefit of being simple, straightforward and having low administrative overhead.