The issue isn't simply the draft picks, it's the money. The value of drafting a guy is markedly higher than signing Turner as a RFA, giving up your first and third round picks (which is a LOT for someone that has never played full time), and losing all of that cap space. Turner is a good, solid player - he is not two of them. That's what a first and third is, a solid or potentially great HB (given how deep this draft is) and a solid or potentially great third round pick. It's a very risky game to give away depth for the sake of frontline starters, especially when you don't have to in the first place. Could Turner be a home run for an aging team that has one or two years left in contention? Yes, easily. But I would say that team is better off prioritizing the future.
When it comes to Jacksonville and Denver, neither of those offices have demonstrated any willingness to sacrifice that so far. Especially the Jags, signing Turner after the Chargers tender him would be the anti-thesis of everything Shack Harris and Jack del Rio have done to bring that team back up. As a Jags fan I hope they don’t, because it would be a mistake.