User blog comment:LegerPrime/Laxus and Cobra's Exceeds/@comment-7418318-20150619174152

The Exceed being sent to Earthland had nothing to do with Dragon Slayers. They were neither sent to kill them, nor to partner with them, nor to bring them over.

The 100 Exceed sent to Earthland were simply evacuated because Queen Shagotte forsaw Extalia's destruction.

That each true Dragon Slayer ended up with an Exceed was just coincidence, as Gajeel and Pantherlily's partnership shows, since 'Lily wasn't even part of the 100 evacuees sent to Earthland. Hell, he was a traitor to Extalia.

Beside that Laxus and Cobra are only artificial Dragon Slayers to begin with, who only got their powers from having Lacrima implanted instead of being taught by a Dragon, so they are different from Natsu, Gajeel and Wendy.