Yes, anyone and everyone should have a right to refuse contracts with the government. Is that difficult to understand? If you find it difficult to understand then perhaps democracy and capitalism isn't for you.
Perhaps. Good luck skipping out on paying your taxes or filling out the census
Maybe, but only in a very idealistic, unrealistic, sense.
Could you imagine a hypothetical where we're at war and a private company has a potentially war-ending tech (nuclear weapon say) that they refuse to sell to the government?