I've found that people don't really care about the legal status of an activity when it's easy to do it without punishment. See copyright infringement as an example.
Then you'll also know that the people care no matter how easy it is far more when the severity of punishment goes up, and if BTC were serious enough to make illegal, then surely (like all serious financial offences) punishment would run high. It's easy to rob a shop, but stealing is a serious crime and barely anybody does it, but many people pirate movies off of the internet and the punishment for being caught is pretty low.