Because if the top 10 had to fight each other over and over, it would be like having a sports league with only two teams in it, playing against each other over and over again. Their win rates and KDRs would normalize to 50%, and these people would just stop doing these arenas entirely.
Asmongold talked about this phenomenon in his Diablo Immortal videos. These top players are likely “whales” because they drop lots of money on PLEX to fund the arena grind. I know that I’d certainly have to be, because I can’t stomach the idea of doing any PvE at all, and arenas are a net loss even if you’re winning considerably more than you’re losing.
Well, the developers understand that the whales need to be kept happy for the good of revenue maximization, so they create a system in which they get fed the “dolphins” or whatever for content. And it’s kind of a “turtles all the way down” system where the dolphins get fed the minnows, and then the minnows get fed the plankton, etc. So we have a system where maybe a few hundred, or even a few thousand, try the arena system every season, but all but 100 or so people are one-pump chumps who get bent over a table once or twice, and then never drop again and go back to running level 4 missions.
If CCP were to add proper Elo-based matchmaking, this fragile system would collapse entirely, and we wouldn’t have any “elites” anymore, because you can’t have elites who are 50% win rate players, since as mentioned before there’s no personal skill involved in the actual arena combat, and all the skill is in terms of fitting your ships and timing your drops.
Real-life sports are similarly flawed, but at least there’s some element of entropy even in those where the competition is in terms of elite-versus-elite, like tennis. Individual sports players still have individual skills and proficiencies, but in video games with gear and items and loadouts it always comes down to the “meta” of what’s the best at any given time, and all of the best players play the exact same way.
This is why battle royale games became so popular. They broke the status quo by adding a lot of dynamic factors and entropy into the element of competition, allowing even average players (like me—I don’t have particularly good aim or “twitch” reflexes) to rise to the top by utilizing unconventional skills and specialties like stealth and psychological warfare. I’ve won so many BR games by throwing some grenades to distract the last guy with the noise, and then came around the back while they pointed their guns in that direction and shot them in the ass. Can I do that in an EVE arena? No, because it’s just a rock-paper-scissors staredown between DPS/kitey/tanky setups where the winner is decided the moment the match is formed.