Why not use a smoothly changing incremental rate? "A steady curve"
First, as it has been clarified that the bracket changes are on incremental income then there are no major discontinuities in the average rate even though there may be in the marginal rate. So one might put the question in reverse: why would you have smoothly changing marginal rates?
I think the big unknown here is how much they'll start to dissimulate and/or offshore their (new) wealth.
According to one paper:
A recent study by Brülhart et al. (2017) gives support to the plausible assumption that the
effect of net wealth taxes on reported wealth is the more pronounced the more integrated
the regions involved are. According to ...
Simeon is correct that Modern Monetary Theory (MMT) is currently being promoted by Stephanie Kelton, who would be the economic adviser for Bernie Sanders if elected by the way.
So what exactly is Modern Monetary Theory?
The basic idea as I have read and understood it is that government does not really need to have any constraint on funding whatever ...