Devil's advocate in me speaking, as someone who agrees that the lack of benchmarks across Linux is disappointing:

It is really hard to make benchmarks for Linux. The systems provide much less reproducible results than on Windows due to how much distributions' settings, tweaks, package versions, kernel configurations / versioning and many, many other factors can cause the results to vary.

Steve from Gamer's Nexus made a great video with some benchmarks they made on Linux, while also describing many of the downfalls and issues they faced whilst performing their benchmarks. Much of this had to do with the fact their process is quite automatic and tooled well for Windows already, and the fact that this process needs entirely re-done for Linux as a whole.

It has to be done manually, meaning these benchmarks can't be done often, and the market share for Linux is still quite small, even if the growth is promising. That being said, since by nature, Linux has no standard, reference distribution for testing; it makes settling on one home for a testing environment that much more difficult. It is very hard to guess what the single most standardized distribution could be for a benchmark. They settled on Bazzite, which I think given their circumstances, made perfect sense.

This is on top of the fact that certain things (particularly gaming) have benchmarks that vary wildly daily. Proton receives patches so regularly across the Experimental branch and forks of itself that it makes tracking issues and solutions down dizzyingly difficult. DankPods did a really great video himself about how rough the out-of-the-box experience of Linux gaming can be for someone who is a novice to this kind of thing, and for someone who isn't interested in doing tweaks and configurations to solve all the problems. That's going to end up being most users, meaning a benchmark that uses defaults is going to be much more impactful and meaningful than one that had to find solutions to problems to even get things to run.

Of course, benchmarks are also important in many other fields such as I/O. I think Michael at Phoronix does a pretty good job providing thorough explanations for the methodology behind each test and providing easily readable charts. I imagine the lack of frequency in doing so has to do with time associated in performing the benchmark itself, just like how Steve mentioned the benchmarks for Linux will be far, far more infrequent than they are for Windows until the landscape isn't shifting so much.