Because they don't give a shit about Bitcoin. They invested in a company. If another coin takes over Coinbase will simply switch to that one.
If you would stop being so delusional and face the fact that the coins you bought at 800 will always be a loss then you can start thinking clear again and look less like an idiot.
Your comment would make sense if all VC capital was pouring into agnostic payment processors . In reality millions are also pouring into Asic manufacturers and mining companies which tech is specific to bitcoin and PoW.
Go through the list of over 528 million in VC capital and see for yourself :
http://www.coindesk.com/bitcoin-venture-capital/Are you really this slow? Do i really need to explain why millions are going in to mining products? No sorry, even a 10 year old can figure this one out.