Why do place names change?

Was just mooching through a lovely old 1836 map of Thanet from the brilliant website Old Ramsgate The Great War that I picked up via the equally nice blog Promote Thanet. I walk my dog most days out at Botany Bay and the name has always struck me as odd. Looking at the map it says it's called Barleymow Bay (that's me squinting and can't really read it that well). It's a lovely name. The Bay then goes round the corner to White Ness and then on to Kingsgate. Which reminded me of the small changes that have come in even over the last few years: The Parade is referred to in the media now as The Piazza and The Stone Pier as the Harbour Arm. Rebranding of place names without good reason sits oddly I think. What's the purpose? It's not as if there has been a disaster, some awful event which makes a name change necessary. Personally, names shouldn't be changed without good reason.