Well, this is less a question for Fedora in general but for the very teams that maintain Workstation, Server, KDE Spin, etc.
They have to be careful what they include, as we have a lot of stuff in our repos but not everything is as well maintained as we want it to be, and the requirements for packages that are shipped by default with the editions are effectively higher than for “any package” in the repo. The major editions select carefully what they include, and usually explicitly ensure its maintenance and proper embedding in the very edition (often a major difference between the official editions compared to, e.g., informal spins - except KDE spin which effectively widely equals a WG but is considered SIG for other reasons).
So including inxi in any edition might bring the burden to explicitly ensure its maintenance and proper embedding throughout evolvement of the very edition.
Problem here: inxi needs a lot of perl stuff that needs to be installed with it, which increases the burden of the very teams if they would include it by default. Afaik, perl packages ain’t the favorites of many people here, and intentionally avoided on Fedora, and adding them by default might cause resistance, although this is only a guess, I cannot talk for these teams/devel people. In any way, we should be careful to assume the implications of having all that perl stuff installed by default.
Personally, I would have not really a problem with it, but someone would have to ensure that all these packages are properly maintained and well tested and embedded with all their configs and so on in the very edition. I assume this will not happen since there are sufficient alternatives available: I never used inxi much, so feel free to correct me, but if I have it correctly in mind, inxi does only accumulate data that is available elsewhere anyway.
So my expectation is that the return on investment is a disadvantageous one.
Supplement: With maintenance, I do not only mean here within Fedora, but also upstream (including collaboration & integration with the very people/teams).