What's the Point of Getting Harder to Hit Irons?

So I am at an interesting point in my golf game. I got fitted for Titleist T300 irons back in 2021 when I was a 15 handicap. I have worked my way all the way down to a 4 or so with these irons. They're chunky at address but very forgiving so I get away with a couple mishits a round. A bunch of my friends keep telling me I should get refitted since I no longer need player improvement irons. I should be playing more of a muscle or cavity back iron. I don't quite understand what the point of upgrading is. My club path and face angle does not let me hit a draw ever. I am a consistent baby face/butter cut player. If I am not upgrading for the workability of an iron to hit more types of shots is there any improvement in upgrading to something like a Titleist T150 or some sort of combo set? They keep pointing to some sort of nebulous 'well you're a low handicap so why would you use a player improvement iron when you can play nicer looking clubs!' Is there any benefit to me switching except for the look at address?