What you're saying is true, but it's also interesting to me that studios could potentially get by with less.

Young Harrison Ford in the late 1970s might have been willing to trade away the use of his likeness in future Star Wars films for a relatively small consideration.

In the future, if a studio can find a relatively unknown actor who wants the work, it's possible they could do with a digitally-produced likeness, in case the original actor doesn't want the job. (Sort of an augmented version of the SNL contract)