This isn't exactly "immeasuable." Balance sheets quite commonly have an entry for "goodwill" and brand/IP valuation is an art in itself. It's clearly difficult to measure, but it can be measured.
On the other hand, while, depending on how liquid the market is for ownership and debt shares in your company, it may be fairly straightforward to place a value on the entire company, with estimates of how to divvy that up getting less clear between individual line items on a balance sheet, attributing that value to specific individuals, roles, and actions is nearly impossible for all but direct salespeople.
This is where the notion of creating value for your customers gets a lot more nebulous. It is entirely possible to actually measure the monetary impact your product and even specific features of that product can make for a customer, and extrapolate that history to estimate the impact of similar products and features, but there is an actual measurement and statistical science to doing this, and almost no one involved in technical project management and certainly not engineers actually have any of the toolsets of accounting and economics to do this, so we mostly just wing it and make guesses based purely on intuition, so we can get back to our real jobs and do what we're actually good at, which is not measuring and estimating value.
And, of course, this gets a lot stupider when you get into government work and nonsense like EVMS, because your customer isn't a profit-making entity that has any monetary value in its operations at all, yet all of our tooling and thinking is based on the premise that value can be quantified via a common medium of exchange and ranked.