Upvote:4
There were actually about 70 towns (by Plutarch's count) named after Alexander, but he didn't found and name all those places himself. He was the founder of the various Greek states (even if mostly by virtue of conquest), so it would be perfectly natural for the Greek ruling classes to want to pump up his reputation, including naming a lot of things after him.
He did in fact found rather a lot of towns though (not all named after him, and many "repopulations" of older town sites). According to the authors there, most were military centers for his soldiers, who weren't realy keen on mixing with the locals.