Salary cap management matters. Jaylon has developed into a fantastic player, but let's not forget the team got nothing in year 1 of the contract, and only average play in year 2. The production or return on investment is important on rookie contracts. The team will have gotten 2 very good (cheap) years of production for a super high 2nd round pick, instead of 4. Would another good player who was actually on the field have made a difference at the end of 2016? Now he will earn elite money. Is the LB position the best position for that, or are the QB or DL positions more important? Where best to allocate elite money?
Cooper is another good example. The team will be paying him handsomely too in short order. The first round pick used on him could have secured a good player for 5 years on a cheap rookie contract. It's not just about talent, but also about dollars. When the team is left without quality depth on the OL, DL, or other important positions, this is why.