I agree, there is no reason for such tools to be closed source, but this looks mostly historic. Developers coming from Windows background were historically les

I agree, there is no reason for such tools to be closed source, but this looks mostly historic. Developers coming from Windows background were historically less open source friendly, or simply didn't even consider such idea, even if they intended for their tools to be used and distributed without restrictions. Another such known example are Windows Sysinternals tools by Mark Russinovich.