Kelly Having 10 coins increases your top speed, each coin you get on the map gives you a tiny speed boost- and the coin item gives you two coins, giving you both a small boost and an overall increase to your top speed. Not to mention having 0 coins makes getting pulled off the level if you fall significantly slower than if you had the 3 coins tax for Lakitu- so while I hear you, and I get it- I disagree, coins have their use for sure.
It blows my mind that people are complaining about this, it hasn't affected my gameplay at all and I barely noticed the change. The whole time I've played, the lure of getting the outfits has been more of a dangling carrot than these UI changes could hope to be.
Great game, 9/10- highly recommend it. Its everything I ever needed animal crossing to be.