Public markets investors typically have far less information about companies than do private investors. For most technology companies, the probability of success / profit is driven more by specific company factors rather than larger industry and macro trends. Most public tech companies are understandably worried about disclosing detailed sales metrics / technology roadmap to all investors for competitive reasons; however, as part of any PE / VC backed investment process, private investors are typically given access to all of this detailed information.
Ah yes so private investors have more specific information while public market investors focus on overall market trends. But is there no way to public investors to get a glimpse of the internals of the companies without disclosure of competitive information? Maybe through some kind of report by a consultancy under NDA, or a small group of investors under NDA giving an investment report?
Under the SEC's Reg FD, public companies are required to disclose all material information to all investors at the same time. So, what you propose is not really workable under the current regulatory regime. Sometimes public companies will give extra disclosure to help investors (e.g., product line revenue, numbers of employees within each function, etc.), but often that information is not enough to truly diligence an investment thesis.
As a result, there is a slight information asymmetry penalty in the valuation; however, this penalty is dwarfed by the liquidity premium you get as a public company.
