Baseball is probably the only sport where you can still compete spending 1/2 the money of most of the league. Allowing the team to decide when you are major league ready and delay your service time until they do pushes the players closer to their prime during most of their time with the drafting team while also forcing them to play for pennies on the dollar initially if they are immediate stars. Compare that to the NBA where you are burning your time with very young players that could be 3-4 years away from being truly impactful or the NHL where you biological age drives unrestricted free agency.