This is exactly what happened with the US federal income tax. It was originally only a small amount, and only on the wealthy. Now it's gradually been expanded to everyone.
> It was originally only a small amount, and only on the wealthy.
This is a bit misleading. The first income tax of 1861 was on incomes over $800, which inflation-adjusted is about $23000. The next year the threshold was lowered to $600 or about $17,000 in today's dollars. Currently the standard deduction is $12,200. Certainly some creep, but it doesn't quite fit the described jump from only the wealthy to everyone, except perhaps to the degree that nearly everyone in the US today is wealthy compared to the average citizen in the 1860s.
Rates have certainly gone up since then (originally a 3% rate), but top rates today are quite low by modern standards - they were higher than today from the 1930s through the late 80s. Typical average rates have been on a slow downward trend since WWII.
I think you are also being a bit misleading, you do mention how much richer people are today but this really can't be overstated. In 1861, only 3% of the population earned more than $800 per year. So the original income tax only applied to the very rich.
