I think you just made my point. Progressivism grew out of the desire to fight economic inequality. Before the income tax, there was little or no mechanism within our government for the progressive movement to use.
The income tax had a singular purpose and a very narrow scope. Before it's institution the progressive movement struggled to find a foothold, because the concept of redistribution would have been viewed as outright Communistic (still is to most). A tax on income once established, like any government mechanism, was sure to grow, and offered the missing tool for redistribution and future progressive policy. i.e. the baby was born.
The income tax was initially viewed as an innocent tax on the wealthy with a very narrow scope, of course, when a child is born, you have no way of knowing if he/she will be a great scientist or a serial killer. The best you can do at that point is give the kid a good name.
And an income tax was not, by the definition of the time, a direct tax, i.e. being laid upon a person by reason the person's very life or existence - like a poll tax or head tax, so NOT, therefore unconstitutional. Since there was a whole lot of confusion, and some serious redefinition of language over time (as shown in microcosm by encrease versus increase) the 16th amendment was deemed necessary to mostly allow the Fed to collect money without having to redistribute equally between the states.
All from one of those "reactionary" judicial rulings....