I think it could be because of mycorrhiza or maybe because of the problem with flowering and seeds. But really, I don't know.

edit: by higher plants I meant Embryophytes

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    $\begingroup$ Welcome to Biology.SE. The concept of higher / more evolved lineages is undefined. You should probably just name what lineage you call "higher plants". Maybe you meant Angiosperm or Embryophytes, ...? $\endgroup$ – Remi.b Sep 15 '17 at 0:44