In addition to the other explanations (it's in the heart of London and not being removed), it's also advancing the government position of deconstructing national identity (for Britons): https://britainmagazine.co.uk/diversity-built-britain-50p/
Anecdote, a close family member of mine is a director of arts for a very large city in the US. They typically install/uninstall at night - she's told me this is especially important with cultural or otherwise edgy pieces.