Why per-protocol analysis matters to investors
When you're investing in any sort of medical technology, you need to really understand how useful it is, whether it will actually have a market, and how that will affect the value of the company. If a company opts to provide only per-protocol analysis, it won't give you a very good picture of what's happening and may even be an attempt to mask problems with the intervention itself.
On the other hand, if you're investing in or examining a company that provides per-protocol analysis and other types of data, like intention-to-treat analysis, you'll get an amazing look into just how the intervention works (or doesn't).