Because Titans desperately needed a good offensive subclass that didn't send them straight into enemy territory just to HOPE to get a kill and then die immediately after. Warlocks had their Nova Bombs that they could use to strike a massive blow from a distance, Hunters had Golden Gun that they could also use from a distance and get many kills while Titans had a defensive bubble and a massive explosion that required danger close proximity to be effective as well as a large congregation of enemies. The risk/ reward ratio was practically 0 unless you got insanely lucky and a mob of enemies or entire fire team was in the same place at the same time. Now Titans have something that has the effectiveness of Nova Bomb with almost the range of Golden Gun which they did desperately needed, imho.