That's certainly
a reason, but Go doesn't have the adoption issues that Swift has despite Google's reputation. Go's GC may be fast, and on some workloads maybe even competitive against ARC - But, I really don't think that has anything to do with why Swift isn't seeing widespread adoption outside of the Apple ecosystem.
Here's my personal opinion for why. Bear with me for a second.
I just searched "Swift programming language" on my search engine and the first result looks promising:
> https://developer.apple.com/swift/
OK. It's a language by Apple, so it's not surprising that it's on Apple's website, even though I think if you want people to get the idea that it's a serious independent project you probably should give it its own top-level site personally. (edit: Yes, I know it does. This is my honest first impression. Please keep reading.)
> Swift is a powerful and intuitive programming language for iOS, iPadOS, macOS, tvOS, and watchOS.
Alright, we're only talking about Apple platforms. Technically it doesn't say that it can't work outside of these OSes, but it's clear that Apple is not marketing Swift as a general purpose operating system. From Apple's marketing PoV, it's an operating system that is made for Apple platforms and anything else is incidental.
> Download Xcode and learn how to build apps using Swift with documentation and sample code.
No download links for users of other operating systems. But if you go to that link, all the way at the bottom, you get:
> Swift is developed in the open. To learn more about the open source Swift project and community, visit Swift.org.
Finally, you might notice that Swift is actually available outside of macOS. It's available for Windows and Linux, but not BSD as far as I can ascertain. The platform support of Swift is excellent when it comes to Apple devices, but it lags far behind other options when it comes to other platforms and architectures.
My perception is that Apple hasn't really made a serious enough investment into making Swift a general purpose programming language outside of its own ecosystem. That's honestly fair, as doing so is no doubt extremely expensive and time-consuming, and it's an on-going investment.
What they're doing now appears to kick it to the community, who has done a lot, including as far as I can tell, make Swift work on RISC-V. But Apple is literally the world's biggest technology company, so it's not exactly desirable to put a bunch of community effort into giving it the on-going support that it needs to feel "first-class" outside of Apple platforms.
Even just the optics here are quite bad, and I think the fact that it's still like this is going to haunt the long-term prospects of Swift outside of Apple platforms.
All of this is aside from its technical merits. Normally, I'd like to stick to purely just technical merits, but unfortunately this stuff does matter. It's part of the reason why Go is still a solid choice today even though Rust has a lot of technical advantages on paper.