Screen reader pedantry, I think; also they're "not semantic markup". The idea was that tables should only be used if the content was genuinely a table.
You're right, it's unnecessarily abrasive. But it is, as far as I can tell, a very minority use case, and these days most of the reader software has adapted. If you see some of the DOM horrors inflicted by Facebook, then suddenly tables look positively readable.
Perhaps what should have happened was the defining of a "table-layout" tag that behaves exactly the same as "table" except it's understood to be for visual presentation only. Flexbox almost achieves this, but for some reason isn't as popular.
