Tables semantically are meant to represent tabular data and using them for layout became “wrong.”

From a practical point of view too, if you wanted to make separate mobile and desktop views just by using different stylesheets, using a table made it very difficult.

(That said, in 2000, if you were using separate mobile and screen stylesheets, you were in an extreme minority because there were relatively few full HTML web browsers on mobile devices. Instead, most phones, if they could access the Internet, accessed a different version of the Internet accessed over WAP.)