Don't Japanese baseball players get drafted out of high school? College sports is more of an American thing. In soccer you get recruited by teams at a young age and play at their academy.
Manga
Yeah, I've wondered about that. College sports seem a bigger deal in the US than in other countries. Overseas you got kids already being trained by pro clubs and high school age kids playing in the pros in places like Europe as opposed to having to wait until they meet an arbitrary age limit or year of college before they are allowed to go pro.
If that's the case then college sports overseas doesn't sound like it'd be filled with potential star candidates, so even less of a big deal than high school if it means those athletes in college have hit their peak so are unlikely to go pro or be part of the national team. Same excitement wouldn't be there, since in the US players as good as Messi would be forced to play in college before being able to move on which is also what makes college sports exciting despite being amateurs.
US soccer players as good as Messi would be recruited by an European team before they even finish junior high.
Not so much for basketball and American football though which are the main college sports that are the main focus of most programs. Guess should have said LeBron, since afterwards the rules changed.
But, that is my point. That as you said guys of Messi's caliber already go pro early. Like how Luka Dončić went pro at 16 compared to players like LeBron who had to wait until he graduated college and then guys like Durant had to do one year of college after the rule change. So it was speaking of the differences in college competitiveness in the states compared to overseas.
Highest paid NCAA football coach makes nearly 11 million dollars because of all the revenue and attention around college sports. It just seems like a completely different level of interest compared to what other countries have in their college sports. It's a giant industry. With of course student athletes not being paid.
High level college sports is quintessentially American
College women aren't taboo.
I would guess the average manga consumer isn't into sports.
I'm no expert on this, but in addition to the other factors people mentioned, I would say that people in Japan seem to pay a lot more attention to high school sports. The Koshien Stadium and the high school baseball tournaments name after it are very famous. I'm not even interested in sports, but I know about them and often notice friends talking about them online. I know absolutely nothing about the college baseball tournaments or where they're held.
Why children in general. I hate it. Just make everyone be 18+ and you can have your pervy moments and not be a pedo (not talking to you op, just frustration at the pedo problem in anime and manga)
Tangent: Any recommendations for sports in a professional setting? Hajime no Ippo is great, but looking for others as well.
Ashita no Joe for an old classic (Megalo Box for a modern take but it's only in Anime iirc). This is Boxing btw
Blue Lock for Football (although still about youths)
One Outs for Baseball (not your usual sports manga, more of a psychological thriller)
Hikaru no Go for Shougi (MC is young but he's fighting professional players, like a young chess prodigy fighting Magnus Carlsen)
I have also been wondering. I doubt there is any satisfying answers to this. It's most likely just a symptom of the entertainment industry in Japan favoring works that have that setting. Similar things happen all over the world, Hollywood goes through phases of churning out media that plays in to pop culture. It's not necessarily nefarious or bad, humans just kinda be in hive mind mode sometimes