The bishop is very active on the a2-g8  diagonal, but the maneuver costs White time, and it often stays on the  road of Black's raging pawns. This is the reason why the English Attack  blossomed at the end of the past century. White wanted to save all the  tempi on maneuvering by just capturing a hypothetically annoying black  knight on c4 in one move with Bf1xc4.
1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... a7a6  6. f1c4 Fischer's  beloved line against the Najdorf has picked up popularity of late. 6... e7e6  7. c1e3  7... b7b5 