* If I many ask what is the major reason while some countries ruling class ban bitcoin transaction?
They are trying to avoid what e-mail did to postal offices, they are trying as much as possible to save their banks from being unwanted, they are trying so hard to keep all transaction activities under their reach as crypto is untraceable.
* what harm does bitcoin contributes a country that can lead to ban?
Used as payment method of illegal arms dealing.
Used to launder money
Used as means of funding terrorism
Crypto is mostly used on the silk road