haha, alot of vocallists do that, they halfcup the micrphone and do vocals into the half-cup.

but no; as an experienced vocallist i know; it just creates a different tone, and it's used for different vocal types and sounds.
inhales and lows almost require cupping.
highs CAN be cupped, but they get way too much gain;
i suggest figuring out with the microphone how to make all of your vocal types at the same volume.

note: cupping gives you gain, reverb, and volume.