You have to remember the Electric Coin Company and the Zcash Foundation are based in the US and is under the authority of many government agencies including the SEC. The ECC and ZFND care about promoting privacy preserving technology and open source software, not boosting investor profits.
If they were to begin trying to “pump” or “shill” Zcash for short term price gains as you suggest then it could be perceived as price fixing/manipulation by a private company which is highly illegal in the US.
Zcash is designed to be a tool for users to transact privately and securely with one another.
(Disclaimer: my opinions are my own and do not represent an official position from the Zcash Foundation)