Why not? Plants like people being around, and they like it when people talk to them. Theorists theorise that it's something to do with either:
1. We generate carbon dioxide and use up oxygen when we breathe, and plants photosynthesising do the reverse. This causes a mutually beneficial concentration gradient.
2. Brainwaves.
3. Plants are sociable organisms, and, despite it being a little cannibalistic, like people being around and having a smoke with them.