Mostly because it's an unpleasant task that can involve large sums of money if you put things in the wrong boxes. And even relatively straightforward brokerage accounts and second income sources start cranking up the complexity in a hurry.

I don’t find that to be true about brokerages. I have 4 different brokerages, and each one sends a well labeled 1099-B/DIV/INT.

Non W-2 or 1099 incomes with various deductions get things complicated though, and I would punt that to an accountant.

I don’t know. But if you’ve opened up the IRS free fillable forms website, and put up the accompanying instructions on your second monitor, and know how to read English, I don’t see how it’s difficult, if you’re income is from a W-2. Everything is kind of labeled and laid out for you.

When I was in middle school (1980s) we did a tax return on paper, I think it was part of a Social Studies class? We were given a fictitious W2, number of dependents, etc. and had to fill out a 1040 and a State return (on paper of course, no computers then). This permanently demystified the process. I think a lot of people who pay HRBlock or similar to do their taxes have never tried to do their taxes manually and are just afraid to try.

I have always done my taxes myself, on paper, even years when I had capital gains, education credits, 1099s, and small business (single member LLC) income. It's a bit time consuming but not difficult per se.

I believe that's only for filing a federal tax return, and for filing your state tax return you still have to either use a tax preparation website or do it on paper.

California has a had a wizard-style site for... I'm not sure a decade or so.

Here:

https://www.ftb.ca.gov/file/ways-to-file/online/index.html

Maybe a bit of an open secret? Found with "site:ca.gov", halfway down the DDG page.

Other little-known, useful USA services:

weather.gov new.nowcoast.noaa.gov

Many states offer online filing systems, might even be the majority now. You just have to visit the state’s tax department website.

Because everyone (for certain values of everyone) has a niche issue that current software doesn't address or addresses poorly, or they just don't want to pay for something that the government should provide. It's their damn tax code, the least they could do is make it as simple as possible to PAY THEM MONEY.