I would say a large reason to the matter is that simply isn't black-and-white or simple enough to have a definite answer and there's very little value for anyone to actually explain why they do that, because as with much communication developers/publishers engage in, it's only gonna draw more backlash, conspiracy theories and just more work for them for no seemingly added value.
But as to the multitude of reasons, here are some that I can at least attest to some people in the industry skewing towards:
- sales data alone these days isn't accurate enough, and especially should not be used for investment purposes and to assess the overarching business outcomes as games have extremely varied sales tails and well performing MTX can easily make a project far more successful even if it carried less initial sales than it's predecessor
- with GaaS other metrics can be more business critical and part of the strategy (why engagement is being used so often) because publishers overall performance can be their catalogues performance and there can be an expectation of singular releases underperforming but overall strategy working when some other game performs well and gets good engagement and recurring performance
- many of these other metrics are valuable to the companies (bringing a potential edge in keeping leadership of their market segment or making better products in the future) and there's good reason to keep them in-house (being a pro-active answer to "well, if upfront sales data is producing a skewed perspective, why not release the whole stack of performance related data?")
- when there are plenty of paid outlets doing better by getting revenue out of these reports (remember us players bring very little if none in revenue to many of these outles) why would you stay open?
- the industry feels much less secretive from the inside and there's fair bit of knowledge to be gained easily, thus a lot of the people already have access to the necessary information from an investment perspective
- much of the actual business and investment critical data is already being provided in investor calls, quarterly reports and whatnot, and it differs little from many other software industry counterparts (in fact you could argue there's far more public data available for games data than in many application/software industries)
- many of the non-investment/development professional easily misunderstand the data, so you could be opening yourself into a ton of unnecessary communication work
...and the list would go on quite easily. But the point is that there is no simple answer that would be already rule it out, but at the same time you can find a ton of somewhat reasonable reasons (
keep in mind I don't personally agree with them all) why many metrics aren't as easily accessible and you can't find all that many in support of making said metrics more visible, at least without it being a business in itself (the likes of NPD, AppAnnie etc.)
