> I'm pretty sure the majority of knifes used for criminal activities are rather kitchen knifes.
Regardless of whether this is true (which it probably isn't, at least in the US), it doesn't change the intent. We regulate different things differently based on their intended use.
This should cover your second question as well. Intent is what the government cares about in this instance. And yes, it is indeed illegal to conceal your transactions from the government, at least insofar as they concern money that the government is entitled to tax or review.
Regardless of whether this is true (which it probably isn't, at least in the US), it doesn't change the intent. We regulate different things differently based on their intended use.
This should cover your second question as well. Intent is what the government cares about in this instance. And yes, it is indeed illegal to conceal your transactions from the government, at least insofar as they concern money that the government is entitled to tax or review.