I am still new to woodworking so pardon me if this is a "too-basic" question..(i googled and could not find an answer)

It seems that when people cutting bevel on long board, they always set the board vertically to make the cut, please see the attached screenshot.

Screen Shot 2021-04-04 at 9.36.34 AM.jpg



I was wondering, why not just lay the piece flat on the tablesaw, tilt the blade to whatever angle needed and make the cut? It seems to be much easier and get the job done? Or am I missing something?