I suspect a large part of it is a SEP IRA which lets you pack away like 57k in a tax advantaged account. Business deductions are almost like icing on the cake vs that.
Deductions sound good to people who haven't actually run a business or thought very hard about it. You have to be purchasing stuff to deduct. As a software engineer why not just not buy stuff since all you really need is a computer. Then you keep 100% of that money rather than 10%.
Some outliers are home office and utilities and things like that.
The attraction of deductions for sole proprietors working from home is not buying new stuff, it is the opportunity to pay for stuff you would buy anyway with pre-tax dollars.
