Free-kick interference? Deal a card

It happens on nearly every free kick. A player on the offending team runs over and stands in front of the ball so the other team can’t play it quickly. Only when the ref intervenes does the offending player move. By then, any chance for a quickly played spot kick has been dashed. Why is this allowed? It’s yet another stain on the integrity of the game. The first time it happens, the ref should warn the offender. If a player on that team does it a second time, that’s a yellow card. That’s one way to root out this cheap ploy, which has gone unpunished for too long.