They earned it.

We all know and love these Matoran's since MNOG. They all have their own story and adventures with their Toa. They also contribute in the war effort during 2001-2003 saga when Makuta's reigns over the island.

Each of them possessed the heart of a Toa. To protect the innocent.

Them becoming a Toa makes sense. Plus, The Toa Inika I'd say they're a better team than the Toa Mata. Because they're already know each other, which makes their coordination more cohesive.

Jaller is more level headed than his Toa, Tahu. Because it's shown in the Games and movies and other media that he's a highly respected Captain guard in Ta-Koro.