The answer is that interval funds do not offer daily liquidity. (nreionline.com)
ETFs differ from mutual funds in that they trade on the stock exchange in the same way a stock does, and they can offer higher daily liquidity and lower fees. (nusenda.org)
Because interval fund managers don't have to provide daily liquidity, they are able to invest in less - liquid, higher - return assets. (nreionline.com)