While I'm not sure as to why specifically Israeli banks are against cryptocurrency, I do believe that this is the general view for a majority of major banks that exist today. Cryptocurrencies are a new type of currency and the banking system is built on fiat currency. Banks are very old established entities and they must limit their involvement (risk) until these technologies have proven themselves to be all they stand for. It is also difficult to track what cryptocurrencies are being spent on and banks do not want to get their hands and feet in muddy waters.