The justices don't vote on "abortion, environmental protection, etc." They vote on the legal vehicles that have been used to address those things. And views on those legal vehicles map onto judicial philosophies that have nothing to do with the substantive issues.

To use an analogy: there's people who think operating systems should be microkernels, and people who think they should be monolithic kernels. Windows NT was created to be a microkernel. But around NT 4.0 they shoved the GUI into the kernel space. If you're on the "Supreme Court of Windows NT," how do you view that? One camp might say, "NT is supposed to be a microkernel, get that GUI out of there." Another might say, "yeah but here in the real world, customers demand a fast GUI so it's fine to cut corners."

Constitutional law is basically that, except we're talking about cutting corners with the highest law in the land.