It’s not hard to see why firms tend to focus on just one mode of resource acquisition.
Each approach calls for different selection skills and implementation capabilities, which in turn call for different cultures and organization structures, and these all take time to build.
Although sticking with one mode may work in the short term, the long-term risk in that the company will end up doing the worng things really well, lagging more broadly capable competitors, and, quite likely, becoming targets themselves.