Why is the sporophyte stage dominant in angiosperms?

In angiosperms, as in all vascular plants, the sporophyte is the dominant phase of the life cycle. This dominance is the result of an evolutionary trend in which the sporophyte stage has progressively increased in size and complexity, while the gametophyte stage has become increasingly reduced and dependent.123

In angiosperms, the sporophyte is the typical, green, photosynthetic plant body that is visible to the observer. Conversely, the gametophyte phase is extremely diminutive—reduced to only a few cells—and is entirely dependent upon the sporophyte for nourishment. This reduction is significant because it allows the plant to protect its reproductive processes; for example, the female gametophyte (the embryo sac) develops while retained within the parent sporophyte's ovule. By delaying the storage of nutrients until after fertilization has occurred, angiosperms avoid wasting resources on embryos that may not develop, a distinct evolutionary advantage over more primitive seed plants.145