It's really very simple -- either publicly supported science is meant to serve the common good, in which case total data transparency is required, or publicly supported science is actually meant to be a vehicle for corporate profits, in which case all scientific data is proprietary and those who share research data are cheating stockholders.
All this apart from the most basic principle of scientific philosophy, in which earnest, transparent efforts to find out which theories cannot be falsified has the highest priority.
I was about to make much the same point, only I'd put it this way :
Scientific research is supposed to be a public good in the economic sense[0]. If it isn't done openly and transparently then it isn't and it most certainly shouldn't be publicly funded. This manifestly isn't how it works currently - see e.g. world v Elsevier et al - and this is really just a plea to retain the broken status quo.
If researchers want their work to be of benefit solely or primarily to themselves or their paymasters - a violation of the Mertonian norms [1] - they can go work in industry.
Incentives matter, of course and what's at the root of this is that scientists - no matter how much or how often they may insist otherwise - are just ordinary self interested human beings.
I'm laughing at your comment because it assumes the data is valuable! In reality a significant chunk of it is made up, this is more about people hiding their arses then corporate profits!
> ... but the problem is that scientists are not accountable.
Arguable, but if they don't have to release their data, then very true -- they aren't accountable. By requiring scientists to release their data, we make them accountable for any shenanigans that might otherwise be concealed.
All this apart from the most basic principle of scientific philosophy, in which earnest, transparent efforts to find out which theories cannot be falsified has the highest priority.