In many cases, any licensing income is earned by a separate but related company that paid the SPHC for the rights to re-license the film (but usually the distributor also acquires licensing rights). The SPHC is generally a profit-participant in the licensing company, but its share of the licensing profits usually varies based on industry politics (i.e., leverage).
A-listers with sufficient leverage and competent representation can sometimes participate in the profits...of the distributor. It's not enough to get gross profits since gross profits take into account COGS/COSS. What you really want is "first-dollar gross", meaning "gross income" before distributor expenses.
For example, say, "Gravity 2" makes $100m at the box office. That $100m is first-dollar gross. If WarnerBro's COGS were $80m, gross profits were only $20m. If Sandra's share of profits was 1% of first-dollar gross, she's looking at $1m; but if she only had a gross-profits participation, she's looking at only $200k. If Sandra was a net profit participant, she wouldn't make anything at all since Gravity Special Purpose Movie-Making Entity has an $X million dollar loss related to production expenses for making the movie and the distribution expenses WarnerBros is expensing to it.
[source: I do this. But not for WarnerBros or Gravity, those are just examples that are easily Googled if you want to follow up with your own research.]
So I suppose one answer is to have good negotiating position.