>The thing we’d be giving up is 2% of our economic output…

That 2% was for a payout of just $1,000 a month and the participants knew it was temporary. A more generous payout that was permanent might lead to a higher percentage.

>...and the thing we’d be getting is, I think, a massive improvement to people’s quality of life.

The general principle of most welfare systems is to provide for those who are unable to work. There isn't nearly as much support in the general public to provide for those who simply choose not to work. Hence the comment in the blog that "...if it’s confirmed that basic income discourages work and provides little long-term career benefits, I think interest in the idea will wane rapidly."