They are not as similar as they seem. In the main line KingsIndian structure with pawns c4 d4 e4, black as active counterplay against d4. Pirc is a less active manovering type of opening. It is more typical for KingsIndian players to choose sicilian against 1.e4. In general to play 1...g6 well need to be able to play a wide range of structures. So not a lazy man's play against anything as might seem superficially.
Should a kings indian player play pirc as well?
TwoMove is correct. I myself combined the KID with the Pirc for the wrong reasons way back, thinking they should be kind of similiar. I soon found I was wrong, but nevertheless I stayed with both for decades, simply because they both are fun. Btw KID and Sicilian Dragon also don't have much in common. There simply is no e4-substitute for the KID.
I agree that the KID and Pirc are different, however knowing both can be helpfull when dealing with some flank openings where White has not committed to a central structure. Kowledge of the KID also helps when White plays 1 e4 d6 2 d4 Nf6 3 f3.
I played the Pirc and KID quite a bit OTB (U1800 and U1600). The Pirc is a real drag, if your opponent plays accurately it's really hard to generate any play. With KID you almost always have the change of launching a kingside assault. I've since traded them in for the Grunfeld and French and am doing a bit better as black
Actually, contrary to the comment about no e4-counterpart to the King's Indian, there is an opening best recommended for KID players. It's the French. I played both back in 2003, don't play either now, but the two openings are extremely similar in that both very frequently feature what is known as the "blocked" center. Both involve virtually the same idea. The center is completely blocked by pawns, and both sides need to follow the "Pawn Pointing Theory", which basically states that if the center is blocked, you should attack in the direction that your pawns point. Therefore, in the Classical King's Indian, White attacks queenside, Black attacks kingside. In the French lines where the center remains blocked (especially in the advance variation), White attacks kingside, Black attacks queenside.
The two openings really do go well together, and any time a French player asks me for a suggestion of what to do against 1.d4, I tell him the King's Indian, and vice versa, I tell King's Indian players to play the French.
They seem to be so close and it would make a repritorie against e4 and d4 does it make sense?