Both gymnosperms and angiosperms bear seeds, then why are they classified separately?

Explanation

Gymnosperms and Angiosperms have been classified separately due to folowing reasons :
(i) Gymnosperms bear naked seeds but in angiosperms seeds are covered with fruit wall ( pericarp) .
(ii) Double fertilization is present in angiosperms which is absent in gymnosperms .
(iii) Endosperm in angiosperms in triploid which is haploid in gymnosperms.