Valorant is my first fps and I'm a bit curious and confused. If you have enough money to buy the guns you want why does it matter? Why's there an eco score?

I enjoy competitive, but I can't play with my friends, because of difference in ranks. So why not make a knockout mode where you can pick 4 other players and play a max of 4 matches to get to the finals. The downside is that you might have...