The exact formula to determine how a team earns compensatory draft picks is not actually disclosed by the NFL, but folks have gotten pretty good at crunching through the data to construct most of the equation, most of which I don’t understand.
The basic gist, though, is that if a team loses more free agents than it gains the previous year, and if those free agents played significant snaps and earned a certain amount of money, the team could be entitled to a compensatory pick. A team can receiver a number of picks equal to the net loss of compensatory free agents, to a maximum of four.
San Francisco signed quite a few big names this past offseason, or at least big enough names that they were not expected to earn any compensatory picks. Robbie Gould effectively eliminated the loss of Phil Dawson.
Pierre Garcon, Marquise Goodwin, Kyle Juszczyk, Earl Mithcell, Brian Hoyer, Elvis Dumervil and others were signed to offset any of the 49ers losses, which included Torrey Smith, Antoine Bethea and not much else outside of players they themselves released.
In summation ....