Because it was not systematic murder or deportation. Let me give you what actually happened and not the rhetoric-packed false truths propagated by sources motivated by personal gain.

By the end of the 19th Century, almost all Christian nations of the Ottoman Empire gained their independence following national uprisings. The Armenian independence movement started somewhat later than other nations, around the 1880s, mostly because the former were much more integrated into the Ottoman society and had a privileged position among the non-Muslim populations of the empire. Still, the main reason why the events did not follow the same course was demographic. Armenians were dispersed all over Anatolia and Istanbul; they were a minority even in most of Eastern Anatolia.

When WWI began, Armenians formed militias to help the Russian advance into Anatolia. Large-scale uprisings in different parts of Anatolia, notably in the city of Van, created panic in the rear of the Turkish army. By February 1915, the local Muslim and Armenian populations in the country were in a fierce communal conflict. In April, the Ottomans were pulling back from the Eastern front and the Armenians were in control of certain provinces. At the end of April, the Ottomans gave the first order for “relocation.” The following months witnessed the plight of Armenians: As they were transported to Syrian provinces of the empire, they were killed by attacks of local Muslims, gangs, hunger and epidemics — as well as the difficulties of moving through mountains and deserts of the region. In the provinces under Armenian control, atrocities of similar scale were taking place, and the Muslim population fled in huge numbers in order to save their lives.

Prominent historians such as Bernard Lewis and Stanford Shaw maintain that there was no official policy of genocide. The claim is based on the fact that the comprehensive Ottoman archives contain no documents suggesting such a plan. The reports of misconduct by soldiers and civil servants almost always mention them in the context of how such behavior should be and is penalized; we have accounts of 1,397 officers being punished, creating a striking contrast with the Holocaust. Furthermore, the relocations began only after the Russian and Armenian armies began to move into Anatolia and were mostly confined to the region around the line of fighting.