Best move versus # times played

b6 ranks 1st or 2nd on 5min Stockfish analysis using the chess.com engine. Hence my original question.
I think your search results are being distorted by a move order difference. After 1.d4 d5 2.c4 e6 3.e3 is a very lame move that is almost never player at master level. In the Chessbase online database, 3.e3 was played in 87 out of 58,000 games. But after 1.d4 d5 2.c4 dxc4, 3.e3 is played relatively frequently. So in the database it looks as it 1.d4 d5 2.c4 e6 3.e3 dxc4 is frequently played, but it isn't
Novice here. I reached the following position and computer analysis says b6 is the best move whereas b6 ranks VERY low when compared to other moves in the Openings Explorer for the same position.
Can someone explain why the 'best move' would not be played more?
Thanks in advance.