Men's fashion currently has no mainstream style that shows off athleticism. Sleeveless crop-tops, with abs and shoulders on display! Shorts with flare for muscular thighs, allowing them to be shorter! Semi-sheer panels, allowing for pecs to bulge! Mesh sections in pants! What's wrong with men showing a little skin for once?
What men are you seeing? Buff shirtless men in 3” inseam shorts and a bulging groin are a staple of every American city in the summer. I see more and more mesh clothing in this heat, although I do live by west hollywood.
Not exactly the same thing, but at least where I live, going shirtless is a pretty common way for athletic men to show that off. Obviously not in the office, but it's very socially acceptable to jog, play basketball, sit on a park bench, or grill shirtless. People then build the rest of an outfit/look around that as a core component. There's a certain amount of explicit catering to that in a section of men's fashion too, judging by their model shoots.
You can sort of get there with tank tops and running shorts. But you do tend to look like you just got back from or are going to a workout.