-- I really think this is an important question and, as Justice O'Connor points out, if we have to ask what's the most plausible explanation for this rule, to reward existing vested interest or to stimulate former new works, it seems to me that it's probably the former.
Justice O'Connor thinks for sure that rewarding existing vested interest is the most plausible explanation.
The context tells us that Justice O'Connor thinks that rewarding existing vested interest is probably the most plausible explanation but does not say for sure.
( z1 think :ARG0 ( z2 person :name ( z3 name :op "O'Connor" ) :ARG0-of ( z4 have-org-role :ARG2 ( z5 justice ) ) ) :ARG1 ( z6 have-degree :ARG1 ( z7 reward :ARG1 ( z8 interest :ARG1-of ( z9 vest ) :ARG1-of ( z10 exist ) ) ) :ARG2 ( z11 plausible ) :ARG3 ( z12 most ) :ARG5 ( z13 explain ) ) :ARG1-of ( z14 sure ) )