It's because people think if they enter bitcoin value will rise again which maybe possible but the very essence of bitcoin maybe possibly gone. I'm saying possibly because what if bringing those banks and institution would also means fast adoption of bitcoin and alts? what if getting them in would mean gaining trust from people that lose faith in btc again? what if having them in crypto ecosystem would mean better foundation for crypto holder and an insight for traditional investor what good crypto can bring to the financial world? just my crazy thought!