Lots of reasons: perception of energy waste of proof of work, misunderstandings such as all coins are proof of work/all coins are intended as replacements for fiat/that you must use centralised exchanges/that everyone who likes it is a libertarian/all smart contract platforms are just ethereum but with cheaper fees and much more,insertion of blockchain into contexts where it makes no sense, hate of money in general due to being anti capitalist, hate of the idea of non-state controlled money, hate of highly speculative nature, hate of VC culture and hate the redefinition of decentralisation to mean blockchain