Uncrewed space missions cost less to retrieve the same information from space, it also has little to no risk towards human life.
Crewed space missions have an enormous cost, due to the tons of foolproof equipment to keep the humans alive.
Some scientist complain that there is nothing better in a space mission than human intelligence, as only humans can prepare for the unexpected. However at the cost is not available for all space missions.
Hope this helps, if you need any more information, don’t hesitate to ask
