I think the reason for this is because DeFi has not yet reached its full popularity and full form in the economy. We have just explored DeFi's loan & loan application, we cannot invest in stocks, pledge assets or use crypto as often as we do with fiat.
Many people see DeFi as a money-making trend of 2020 in the crypto field, they don't even want to learn the true nature and value of DeFi.
DeFi is still just a new seed to sprout, it takes more time for the community to know that it is a tall and healthy tree.