Right. For most people that are on a payroll and maybe have a 401k and what not, tax preparation should be easily automated. In some EU countries, the government will send you a draft that you basically just have to sign and send back. For the remaining 20% (likely even less than 10%) of people with more exotic investments, it is probably safe to assume that they either have the knowledge to handle the edge cases themselves or the wealth to pay someone to do it for them.
It should also be noted that the IRS already has all of the information about you anyway. Your bank, your brokers, etc all send copies of your financials to them. At that point, filling in a tax return by hand is basically a potential form of punishment for not doing your homework right.
In the UK 80% of the population don't even have to sign anything and send it back. The rest have some employment income information on a website and have to supply the rest of the data, I found it pretty straight forward when I did it for the first time.
It should also be noted that the IRS already has all of the information about you anyway. Your bank, your brokers, etc all send copies of your financials to them. At that point, filling in a tax return by hand is basically a potential form of punishment for not doing your homework right.