Here's why:

* Gametophyte: This is the haploid stage in the plant life cycle that produces gametes (sperm and egg).

* Sporophyte: This is the diploid stage that produces spores.

In nonvascular plants (like mosses, liverworts, and hornworts), the gametophyte is the larger, more obvious, and longer-living phase. It's responsible for photosynthesis and is where reproduction occurs. The sporophyte is smaller and dependent on the gametophyte for nutrients.

In contrast, in vascular plants (ferns, gymnosperms, and angiosperms), the sporophyte is the dominant stage. The gametophyte is reduced and short-lived, often only existing as a few cells.