In Clash of Clans, controlling your trophies is very important because:

1. To rank on the leader boards: Your Clan, Top Clans, Top Players, My Leagues,…
2. To stay at the most relative league for you to farm. You can read more about this at: [Best leagues for farming][1].
3. To join a Clan (it requires a minimum trophies to join).
4. …

Source: http://cocland.com/guides/trophies [1]: http://cocland.com/tricks-and-tips/best-ranges-for-farming-in-clash-of-clans

In Clash of Clans, controlling your trophies is very important because:

1. To rank on the leader boards: Your Clan, Top Clans, Top Players, My Leagues,…
2. To stay at the most relative league for you to farm.
3. To join a Clan (it requires a minimum trophies to join).