Because it uses these deep integration APIs, we're only allowed to distribute the application using the macOS App Store (whose rejections, appeals, and eventual acceptance made for quite the stressful saga over the last week and a half)
Imagine having to get certified by the Linux Foundation, under distribution clause, to access native Linux kernel APIs. But that's what the developer of Wiregaurd has to do to gain access to native macOS integration.
[1] https://lists.zx2c4.com/pipermail/wireguard/2019-February/00...
https://github.com/MicrosoftDocs/windows-driver-docs/blob/HE...
Yeah, unfortunately it seems like we're still in the state where UNIX/Linux can't popularize anything, especially themselves, unless they're repackaged by someone else :(
Which is absolutely true of Microsoft as well. The sheer productivity boon that Office has added to businesses around the world is unmatched by practically any other piece of software ever written. Most of the businesses would still exist, but they wouldn't be the same business. Excel, Powerpoint, and Word are ridiculously important software.
Apple makes Microsoft look like an angel. Using this argument, Microsoft could claim they could have made hundreds of billions if they got a cut out of every Windows app sale. Oh, and that those companies wouldn't exist if it weren't for Windows.