You want nothing to get between the ball and clubface

When I worked as an assistant in 1962 in California I got the chance to see the results of grooves versus no grooves on Iron Byron , a machine making a perfect swing at the Golfcraft ball and club plant in Escondido. Titleist bought the company, Golfcraft had incredible persimmon heads, no need for staining just clear lawyer. They had “Scotty” the great wedge maker from Scotland and the first most perfectly round ball. They used a marble in the center, instead of a liquid center and then wound around the marble. Now the groove debate. the wedge without grooves spun just as well as the ones with grooves. The reason was the face was dry raw unfinished steel the ball bounced off it normally and stopped quickly on landing as though it had grooves. When we put Vaseline on the face the ball skidded off the face with no control like tires on ice. There was something between the Ball and face When the ball hit a grooved wedge , wet or greasy, the ball would grab against the face the grooves displacing grease grass or water and act normally with control. So In rough or wet dewy grass you need grooves ball hits against the face because of grooves, acting mostly normal.

So keep grooves totally clean for best performance. If you have no grooves it had better be dry conditions and not in the rough. You want nothing to get between the ball and clubface hence deep grooves.