I didn't and nor did my girlfriend. We're both Inheritors and earned over half of our credits from playing either SWAT and Halo CE Anniversary Team Slayer.I think the question is more about why do inheritors continue to boost in grifball. Not...did you boost in grifball to get your inheritor.
Also, I can't stand Griffball. It's the one sure fire way to get me raging in no time
Probably either so they can brag they 'earned' (Which they did not) excessive amounts of cR that they cannot spend anymore, for personal satisfaction of griefing other people's games, or the 'Bro' (What I call the CoD) mentality (Like "Yo Bro, we boosted to Inheritor here man. Bro, this is our playlist. Let's keep going bro! It's the best playlist ever Bro."). Those would be the only three reasons that make sense