How different is it to inventory tracking?
The advantage of calculating capital gains (and thus know capital gains tax due) is the business can optimise the capital gains for their individual circumstances.
In contrast a broker just calculates one of the possible capital gains reportable (typically FIFO which maximises capital gains tax payable for most investments, so is the opposite to what most business would actually like to do).
It’s similar hence lubos wanting to get inventory right prior to fixing investments.