No, I don't bet on cards because I don't know much about the referee. Maybe some people see it is interesting as they know the referee. I think that need more research to know the referee and how they perform leading the match. I just feel that could be more difficult to collect the info about the referee than search for the team info because we already familiar with that.
You're right, because I remember trying card betting before, and it didn't work. At first, I tried to find information to analyze the possibilities a little, but it seemed difficult to find. Furthermore, I thought that card betting could also be analyzed besides looking at the referee, namely by looking at whether the two teams that will be playing are rivals or not, because I think it seems that if there are rivals playing, then there is a possibility that it can be predicted. Even so, I still feel unsure whether I will try card betting again or not, because it is the same as the number of corners I have done, which is difficult. Currently, I still feel comfortable with betting on the favored team, even though the odds are usually not that high.