3rd parties convince you taxes are complex via underhanded tricks, but that doesn't mean they are. There is a reason tax software puts lots of delays in - they want to you think your computer needs time to do the complex calculations. There is a reason tax preparers interview you and then don't give you the taxes filled out instantly - they want you to think there is a lot of hard work left. Has your tax preparer ever told you that some tax deductible things are not worth deducting or did they just look at and ignore the receipt - that is a way to make taxes seem complex.
If you own a small business your taxes might be complex. However most people have been fooled into thinking their taxes are harder than they really are.
I'm guessing it's far more about the rise of shopping mall tax prep than Intuit lobbying.