I think that's because _in practice_ people don't waste their time working on intractable problems if they just want to get something done. There's almost alwa

I think that's because _in practice_ people don't waste their time working on intractable problems if they just want to get something done. There's almost always some way to avoid the intractable problem and approach it a different way. It's sort of like how "in practice" it didn't matter for thousands of years that nobody understood electricity. Any problem that came up that would have required that knowledge to solve just got dropped, because they didn't have the tools to solve it.