I have explained this on several other servers. Many of the older servers most accomplished players already know this.

Specific amounts of medals drop every 24hrs on a server. Say your server has 30,000 players and only 500 lion medals drop. You have 30,000 people farming for medals of that type or valleys and NPC's that might carry that medal. Your chances are going to be low for getting said medal.

The more people that require different medals the bigger variety of medals needed on your server the easier it is to get the medals you need. Why? Because only a certain amount of each type drop every 24hrs and only the most prolific farmers will get them before everyone else.