Player development methods among baseball, basketball, and football differ widely.
The primary thing about football is that size is critical. Nearly every player needs to play 4-5 years of college football just to grow up to be big enough to meet the needs of the NFL.
Another problem the NFL would have if it developed a minor league NFL is that no one would watch. You would still have the great college rivalries and you would be stuck with young guys, hoping that they don’t get hurt while playing for $50K a year in a backwater before a crowd of 2000 people.
Baseball’s tradition of minor leagues and farm systems dates back to the 1920s and Branch Rickey. And even before that, many minor league teams had informal arrangements with major league teams. The amateur draft in baseball is set up so that very few fourth year (senior) players are ever picked.
Basketball allows players who are just out of high school to get drafted. But in basketball’s case, this isn’t as much of a disadvantage in the sport. Most of these players are already tall enough for the NBA. But their games aren’t refined enough yet to play in the NBA. This has caused the quality of NBA basketball to decline as well as college basketball as most of the best players never play college ball (such as Kobe Bryant) or leave early (too numerous to mention).