If the labor force could opt out of the rat race because they didn't have to work, then they gives them immense power especially considering what they have now. Of course the necessities would have to be controlled in a not-for-profit manner so that you can't just have some land baron that adjusts the cost of rent and food upward to ensure it eats up all the UBI, same with utilities/internet/etc.

But for consumerist goods that people want because they enhance life, if people could realistically withhold their labor unless the capitalist offered equity etc in industries that produced those things, you would quickly see the power of the leaders of those industries wane significantly.