I got a catalog in the mail for a company called "Bonobos" that sells men's casual wear and swim suits.

Interestingly, the company offers short swimming shorts more like the 1960s vintage trunks.

Check them out here:

www.Bonobos.Com

Here's an update on this topic.

A friend and I were riding home along a large street here in San Francisco and there's a wide tree covered jogging lane off of the side of the street.

I noticed a group of about 12 young men (probably in their very early 20s or possibly late teens) were out jogging in some kind of group run. All of them were in 1980s vintage running shorts.

My guess is they were part of a track and field team from a nearby college or a high school. Where ever they came from, it was great to see the traditional running shorts back in style. :D

Here, too
 

After seeing this topic, I realized that I have been seeing more casual "short shorts" on men, here in ultra-conservative Utah, lately. Seems to be a growing trend, here, as well as elsewhere.

I would not be surprised if the company that makes Chubbies helped instigate the return of the men's short short to the US. When they first launched in 2011, their motto was 'Sky's out--Thighs out!" and, I just saw on their website, today, an update to that thought, "We believe in the right your quads have to a life of freedom and sunshine"!

They are a bit pricey, but, obviously, their sales have continued and grown, contributing to men wearing shorter shorts. You may want to check them out, if you haven't already.

https://www.chubbiesshorts.com/

I haven't been near that 1-1/2 mile long running track that goes around the waterfront in San Francisco.

However I've gotten a glimpse of the section that runs past the super market where I shop and I see a lot of guys out in traditional running shorts. Those shorts look like they are Nike, Adidas, or some other popular brand.

So if you want the pre 90s style, they're definitely out there!!! :D

Columbia shorts
 

I like the Columbia ones myself:

https://www.amazon.com/gp/aw/d/B0089...ID=71VcBILSRgL

https://www.amazon.com/gp/aw/d/B00ZV...MTMD1JDDT&th=1

Seems that rugby has the most "abbreviated" uniform for dry land sports:

http://www.therugbyleagueexperience....17-final-only/

You are looking at rugby league, a northern British alternative to rugby union which uses short but not quite as short shorts as rugby league shorts.
http://www.englandrugby.com/
I had to play rugby union at school in the 1970's when our shorts were even shorter.

For even shorter shorts look to Australian rules football.
https://www.bing.com/videos/search?q...48&FORM=VRDGAR

Australian rules football
 

Also noticed that unlike soccer or rugby, the men wear sleeveless shirts.
Do you know if there is a reason for this?

Australian Rules Football is a fast game played on a big pitch in a hot climate.
Rugby (Union and League) and Football (Soccer) are winter sports intended to be played in British drizzle and sleet. Hence the long sleeves and rugged cotton or nylon shorts.

In Rugby Union there is a lineout when the ball goes off the side of the pitch. The ball is thrown in from the sideline by a player into a line of players from each opposing team, each side lift one of their players by their shorts to gain extra height and catch the ball in the air. The player lifted up may wear special shorts for this purpose:
http://www.morrant.com/rugby_shorts/...s/54467_p.html

Another possible reason is Aussie Rules “footy” is a combination of sports including basketball, rugby (of course) and soccer, all played on a cricket pitch. The uniforms kind of remind me of old school basketball unis in the US, but a bit more minimalist even.