Why aren't 1.e4 g6 2.d4 Bh6, and 1.e4 b6 2.d4 Ba6 considered by theory? As the title above, why aren't 1.e4 g6 2.d4 Bh6, and 1.e4 b6 2.d4 Ba6 (or eventually beginning with 1.d4) for Black not even considered by theory? Isn't the eventual early trade-off of White's strong Bc1 and Bf1 for Black's Bishop an asset for Black? What is the best reply for White vs such irregular defences? Should he trade the Bishops or avoid that? (i.e. with f2-f4 and c2-c4)?
White should trade bishops and use the unprotected knight to gain some extra tempo and gain a massive lead in development, e.g.

[FEN ""]

1. e4 g6 2. d4 Bh6 3. Bxh6 Nxh6 4. Qd2 Ng8 5. Nc3


4... Ng4 is best met by 5. h3 Nf6 (forced) 6. e5 Nd5 7. c4 Nb6 8. Qh6 and Black has problems completing his development, though there is no forced win at the moment.

I haven't analyzed the b6/Ba6 lines but I guess a similar concept holds.