The digital ground seems to shift weekly. While firmware and software updates over the Internet somewhat slow the constant upheaval, when you do buy something, you just
know that as soon as you plunk down your cash, something new will come along.
So, especially with preamplifiers, why not produce a design based on modules that the user can swap in and out, to custom-configure the preamp to that user's current needs while leaving room for later expansion? Why pay for six inputs' worth of stuff when at present you need only two? Upgrades? New features? No problemswap out a module. Or, if a circuit in one module malfunctions, you can send only that module back for repairs, not the whole thing.