They cannot do everyone's taxes since what they know about many individuals is incomplete.
> should we really have that little privacy?
Put that way, the answer is no. On the other hand, virtually everyone demands services from their government and very few people want those services to be transactional (e.g. most people demand roads, few people want to pay based upon their usage of those roads). That means the government needs some form of revenue. For various reasons, it has been decided that a person's income should be a portion of those revenues. In order to ensure that people are paying their dues, the government needs to collect some information. Are there other ways the government could get revenues? Sure, but all of them are going to be problematic in some form or other.
> Of course, those ideas, liberty and privacy, small government, etc., isn't really fashionable with the latest generations and most people would gladly give up their freedom and privacy to save having to fill out some paperwork.
One has to be careful about generalizations. Even though a desire for liberty and privacy may be universally appealing, we would find that people's views on what those terms mean varies from generation to generation and from individual to individual. Note that I said the meaning changes, not a person's desire for it. As for the desire for small government, well, some people want small government and other people don't. It is a far less universal ideal.
