It's not just the money. I don't see why they would put a guy in there with 120 college snaps at ILB in his rookie season when you are paying a vet $6m.
When your current box safety is a 5th round pick with about 300 snaps at the position that most suits Simmons for now. At box safety he can cover TE's and WRs and be in position to stop the run and on some plays where you might want Simmons range deep you can flip him with Budda. Similar to what the Chargers do with James.
You can have Hicks, Campbell and Simmons or Hicks, Simmons and Thompson.
I know which looks best to me.