buffnut453
Captain
Because its more realistic. So your opponent over claims by 100 maybe 200 %, one's own losses are double overall because of non operational reasons.
You need to measure multiple things during a campaign. From a logistic perspective, you absolutely need to measure total losses to ensure that replacements can keep pace with overall wastage. However, that does not give you any indication of how you're doing on the field of battle. Kill/loss comparisons are a rather blunt tool to do that but it's easy to understand and, during the Battle of Britain, helped keep the population engaged in fighting that, although right over their heads, they couldn't really see.
I still take issue with your use of the term "lie" in this discussion. Overclaiming was rampant on all sides during WW2 but that doesn't mean everyone was lying. Similarly, the use of combat losses as part of a kill/loss analysis is a reasonable way to measure operational success but it doesn't mean that the British Government or the RAF was lying.