At first it was because of what I believed in, and I felt as though I would be supporting what I disagreed with by going inside.

Then... it was because Team Plasma wasn't welcome in most centers after rumors started to spread with what they were doing.

After that... I didn't feel it was right, after what my father had almost done.

If I was being perfectly honest I only ever set foot in a center once, when Zoroark was badly hurt by a wild Pokemon I couldn't seem to reach. He was so feral even his thoughts were unclear to me.