Because regardless of what position is theoretically more "valuable", there would be ONE player in all of baseball with a higher OPS than Yo at 2b, Jose Altuve. Roster construction wise I'd love to have the pinnacle of 2b on our team and sign a slugging 3b.
Nick Madrigal does not slug, as good as he might be one day. Look at how, why, and what teams are winning with now.