Really the only athletes that can’t go pro right out of high school are football players who want to play for the NFL. The NBA currently has a 1 year rule, but previously allowed direct entry (LeBron). All the others who want to go play professional baseball, golf, skiing, swimming can do that. No one is forcing them to go to college or play for the college. The Olympic swimmers had to decide whether to take the pro money or swim in college. Several of them picked college. Missy Franklin gave up millions of dollars to swim at Cal for 2 years because she wanted the college team experience. Tiger played at Stanford.
Even football and basketball players have other options - Canadian football, European basketball. If they are so wonderful, Nike or Adidas could just pay them the $100k to sit out for 1-3 with no college necessary They could have a little professional camp and just sign them to contracts. There is nothing illegal about that, it just makes the player ineligible to play for an NCAA team.
There are just a few players who have won the Little League World Series, a college championship, and a MLB World Series ring. How cool is that?
Earlier someone said that most players at the D1 power conference level play in college with the pros as a goal. I disagree. Even on those 105+ football teams, only a few have a chance at the pros, and in other conferences fewer than that. Thousands of college athletes know that their playing days will be over at graduation. And they are fine with that. They are there for the education and the fun of playing. Some even give up the pros to stay in school and take a Rhodes scholarship or go to med school.