User blog comment:Sargenttacos115/The side efx of Dragon slayer Magic/@comment-4820738-20131109145241/@comment-7418318-20131109152943

If it's the actual act of bathing in the blood, regardless of whether the Dragon Slayer was involved in the killing (maybe even donated/stolen blood of a still living Dragon?) it'd be theoretically possible to get more Dragons by that method, but generally I agree.

Even if a few Dragon Slayers do turn into Dragons, they'd still have reduced the total numbers of Dragons by a massive margin before transforming.

Besides it was never the "job" of a Dragon Slayer to indiscriminately kill all Dragons. They were created to fight alongside one Dragon faction against another Dragon faction, so creating pro-Human Dragons would not go against their reason for existing.