They will usually not get any dividends from the underlying securities - they are invested in derivatives rather than directly in shares - and if the counterparty (or, as is increasingly the case, counterparties) fails they will get nothing. Where the products are Ucits III compliant, even in these latter cases there is collateral that might protect the original investment.
The point is, not all of them will provide a positive return, most will struggle compared to equity alternatives providing regular income and some will even provide a real terms loss. But for a particular client the protections available, if the risks are understood, can be a useful portfolio tool, with the potential returns a tasty cherry on the top.
So don’t write the whole sector off - these two plans prove even assuming the word Keydata being associated with a product is a guarantee of poor outcomes would be folly.