They scatter their matter through unimaginably vast distances in order to bunch up more matter and make new star creatures. Nebulime are in a state of constant growth, their children continuing the process further across eons. Like a slime mold, gathering & consuming matter around it to power its own spread. Since they're hundreds of light years in size, this growth is unperceivable with our diminutive lifespans!
by AphidKirby