This allows you to play effects that only activate on summon, all during their turn, such as Black Rose Dragon which can blow up the entire board
A good example is to build what's called a Menger sponge, based on hollow cubes that can be assembled to form even larger cubes with their own gaps in them to keep up the pattern
This has a rather unique factor that, unlike Grapha, focuses more on Gates and that end of the plussing rather than taking away your field presence
Rally at the Hornburg often outshines Shadow Summoning, but in the games where flying is relevant, the difference is remarkable
Combined with the new Illusions, this can make mitigating damage while collecting Lore somewhat of a breeze
The answer depends entirely on era and rarity