"What makes us so confident that plants don't also meet this criteria?" Brains or other possible organs for processing information are metabolically expensive

"What makes us so confident that plants don't also meet this criteria?" Brains or other possible organs for processing information are metabolically expensive to operate and entropically expensive to maintain the genetics required to build them. If there is no evolutionary advantage for plants to have sensations and emotions, they will not evolve the machinery required to have them.