As title above states, why isn't the "English Attack" popular vs. the Sicilian Kan? I mean the White setup in the Open Sicilian with Be3, Qd2, f3 and eventually g4 and h4. As far as I know, it is fairly popular vs. the Najdorf, the Scheveningen, the Classical, the Taimanov, and the Dragon (in which case it is named "Yugoslav Attack"). But vs. the Kan, almost nobody, at least at top level, plays it. Is there a specific reason for this fact, or it is just a matter of "fashion"?
The English attack is only true mainline for the d6 Sicilian. The reason behind this is that in the e6 Sicilian variation, it's a lot easier for black to pressure your center and break through with a quicker d5. Specifically, black can play a fast Bb4 (pinning your knight and therefore influencing the all important e4 and d5 squares), and break out with d5.
[FEN ""] 1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 a6 5. Be3?! Nf6 6. Nc3 Bb4! 7. f3 O-O 8. Qd2 d5!
Even if black is worried about the pawn structure changing with white playing e4-e5 after d5, then he is fine too if he plays Qc7 instead of O-O to cover the e5 square. Regardless of the exact move order, as soon as black gets in the d5 break, then it's black who is slightly better out of the opening, not white. This English attack setup is too slow against the Kan. Instead of Be3 and a later f3, Bd3 is often used to defend the e4 point and avoid most of the sting out of the Bb4 pin.
While NoseKnowsAll has a great answer, there is a little more, and it comes down to this one thing: It is just impossible to play a good version of the English Attack due to Bb4 by black at the right time.
Even if you are careful about move order, and play Nc3 first, and then Be3, and Qd2, it is still very dangerous to castle queenside. It is easy to see from the diagram below, which is a valid line, that black is doing well if white castles long as intended, and Bb4 may be a part of it. The counterattack comes in pretty fast, and white's winning percentage in the position is only 46.6%.
With a pawn on d6, black does not ever have that possibility.
[FEN ""] 1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 a6 5. Nc3 Qc7 6. Be3 Nc6 7. Qd2 Nf6 8. f3 b5