I wouldn’t rely on JetBrians survey to tell the whole story for C++. TONS of places use Visual Studio for C++ and would never even know about a JetBrains survey
I think my experience correlates with the study. Most lower level code that I had seen used neither unit-tests nor any good structuring. At least in close-to-hardware projects that seems to be more the rule than an exception. I think this is due to many contributors there not having a pure software-engineering background. Those often have not worked in other higher level stacks and therefore are not familiar with practices.
https://www.jetbrains.com/lp/devecosystem-2019/cpp/
34% don't use any kind of unit testing.
35% don't use any kind of static analysis tooling.
36% don't use any kind of guidelines.