I know why they did it. To prevent holding on NMs and other mobs.

This is what my linkshell did 1 day in FFXI.

Had a 8 person team fighting Nidhogg.
Had a holding group claim King behemoth
Had 4 people holding Tiamat with a mule used to pull adds.
And had 2 people holding Sandworm..

So basically my linshell was holding/fighting 4 hnms at once.

In FFXIV the claiming system prevents that. Basically I see it as a step to prevent large endgame shell from monopolizing the NMS and such.