In short, yes it completely makes sense to keep searching for Dark Matter using Earth-based direct-detection equipment.
Even in the case that there is no significant amount of dark matter in the Solar vicinity, that is the only area we are currently able to search using direct-detection. So it makes sense that if we search for dark matter (and we should search for dark matter because finding would be immensely good for mostly all of physics) we should search for it in the only place we are able to.
But that doesn't mean we shouldn't switch to space-based searching right? Yes and no. No doubt, a space-based detector would have a greater range of testing locations and less ground-based interference sources. But that's about all the benefits. Remember that we expect dark matter to be very weakly interacting if it interacts at all. This is why the Earth-based detectors are deep underground and/or heavily shielded (much like neutrino detectors when you think about it). In space, the amount of shielding a detector can have is limited because shielding is heavy and heavy is expensive. Plus there is a lot more radiation and sources of interference in space than on Earth. Plus, typically, space-based sensors never begin to rival the sensitivity of Earth-based ones (that is, the technology doesn't rival it, the sensitivity could be better if space produces less noise in the data, but it won't in this case). Also, and again, it's bloody expensive to send stuff into space and retrieve the data. For the price of a low sensitivity space-craft, we could build a much better detector on Earth. And the amount of dark matter within the areas in space that we could position such a detector is probably about the same as the amount here on Earth.
But, and this is strictly for the record, let's assume that there's some small isolated pocket of dark matter that we expect to find in Earth's L2 point around the Sun. Should we build space-craft and equip detectors and send them there? YES! Should we stop building or even using detectors on Earth? No. Why would we? What if we get no detection from that pocket? Or what if we don't want to constantly send out expensive new equipment? We can do both, build space detectors and use Earth detectors. So even if space-based detectors might give us a higher chance of detection, it would still make sense to keep using Earth-based detectors.
So in short, yes it is completely sane; it makes sense to continue searching for dark matter on Earth. We can't position a direct-detector very far from Earth. We need a direct-detection eventually, so we should keep looking. And space-based sensors are more expensive, less shielded, harder to maintain, and have more sources for false positives than Earth-based sensors.
The science may say that we shouldn't expect to or it isn't very likely that we will find dark matter around here. But until we have any better options (and given that we have to search), it still makes sense for us to search on Earth.
