If you had Flash enabled on a blog or other site that just happened to pop up a flash ad, it would make the whole page janky, greatly hurting pan and zoom functionality and killing your battery life for no benefit.
Worse than this was sites that used Flash in non-essential ways like ads. Flash games and applications almost worked, although virtually none of them were responsively designed, and they mostly worked pretty poorly with touch controls, and unlike HTML there was no way to reasonably work around or improve this at the browser level, because it was just a big proprietary black box. I was an Android user at the time and the only way Flash on my device could be described is in terms of locomotive incidents.
