Why do ferns grow out from another fern?

Mother ferns, Asplenium viviparum, and A. bulbiferum, are two species of fern where small clones grow directly from the fronds of the parent. When the clones are large enough, they fall off the parent, and take root in the substrate below. Many plants have evolved the ability to produce clones of themselves in order to spread faster in an area than their competitors,as reproducing through clones is much faster than sexual reproduction through spores or seed.