It's simple.
SA means not only for enemies, but also for the overall condition which you are at. Surely, if a pilot does not know how many friendlies are around, how many are seeking after the same target you have at your gunsights, who seems to be able to kill the enemy fastest and etc, he's just as unaware as any who is target fixated.
The more such things happen, it just means that the people one is flying around with is in an uncooperative, unfriendly, unorganized, chaotic situation.
As an example, yesterday, a small band of Rooks fought at only 7 miles northside of enemy base A43. Our home base was about 20 miles away at A42. Luckily, among the 9~10 Rooks who were furballing at low alts, so close to the enemy base(which looked like at least 15~20 enemies were stationed), a lot of them happened to be experienced pilots who knew how things were happening around. We fought off at least 4~5 waves of same enemy guys spawning over and over again, in planes like 190s, F4Us and 109s at low alt furballs. The enemies were La-7s and Yak-9Us, N1K2s.
This was possible because everybody was aware what was happening. Nobody did stupid things like targetting after an enemy which another friendly already aquired and was chasing after. We were always looking around, judging which enemy to chase, which enemy to avoid, whom to assist in attack, whom to help in defensive and etc. If everybody was so conscious on getting kills, not knowing what other friendlies were doing, none of us would have survived.
Knowing where your friends are is as important as knowing where your enemies are. If you are aware of this, you would not make the mistake of shooting at a friendly as he jumps in front of you. If your friends are aware of this, he wouldn't do a stupid thing like jumping in front of you either.
All in all, it has a lot to do with cooperativeness and awareness. When sufficient, there is no reason killshooter would bother anyone. When it is not sufficient,

, yes, it bothers someone. After all, as Wotan said "it works as it is designed".