This have evolved over time. Football players do struggle with life changing injuries in bad tackles. Since it is a game played primarily with ones feet a bad tackle may cause horrible leg injuries, smashed knees, etc. And there is little protective gear that works without hindering the players performance. So in order to reduce injuries there is a very strict no-contact policy that is enforced very harshly. This is to ensure that players pull out of potentially risky situations. The problem with this is that it is very hard for the referee to judge if there were contact or not and how hard the contact was. One of the few things they can look for is how injured the player is. If they are rolling around in pain it was probably some hard contact. But this is of course open to abuse. Players can fake injuries to get other players penalized. This is of course not allowed either but it is hard for the referee to judge these things. And when they need to enforce the no-contact rules in order to prevent injuries they do more often judge in the favor of the seemingly injured player.

People are working on reducing this issue though. It is possible to use camera replays to catch things the referee did not see. This does however take time and either slow down the game or is only available after the situation have been resolved. The cameras might not even catch the incident well, if the match even have a full complement of TV cameras. But it can help to give referees some advance notice for the next match. Or the players might get penalties between matches.