Why is it useful to convert ratio to percent?

Answer 1

Percents are a way to express parts of a one whole thing. We can think of 50 percent as half of a whole thing and 25 percent as a quarter.
It is much harder to look at a ratio and see what part of the whole it is. The ratio 1/2 is the same as 50 percent but many people have an easier time picturing the percent.

Also, percent is independent of units and nice to use for things like interest, sale prices, and many other things.