Of course there will always be people who cannot work. But the point is, BI is a basic income for anyone. No strings attached, Here's OPM, even for people who could make a living without BI. Strikes me as a waste of taxpayer's money?
Even if it winds up costing more I don't classify giving everyone the freedom to live their life in a way of their choosing ultimately as a waste. Hell that's the basic utopian dream from Star Trek, Culture or a thousand other places, so much wealth that anyone can do anything with their lives and it's a rounding error. Are we there, no, but we have the surplus to take care of everyone's basic needs today.
Just because the government wastes money some places doesn't mean they're incapable of putting it to good use in other ways or that we should avoid good programs just because they might misspend savings from it.