What purpose do ticks have?

On Wiki, I learnt that ticks do in fact have a few enemies but they are few and far between. As we live on the edge of a forest, ticks are a daily problem from March to October. Luckily we humans have very seldom been bitten by them, I think I have only had one in the last 10 years, but the animals, including the horses, often have them. This example was on the ground having filled itself on one of the animals. Two of the three cats have ticks on a daily basis as they always go for a walk in the forest & the dog tends to pick them up when he accompanies the horses when they go out for a ride.
We treat the cats & dog with a fluid which helps but this year, my wife bought a "tic-clip" for the dog which is attached to his collar. It's nothing more than a metal ring and is supposedly "charged with BIO-Energy". I laughed when she came home with it. Another nonsense gimmick for animal lovers. HOWEVER, after 3 months of use, I have to admit that Flash has had significantly fewer ticks than normal and I slowly am having to get used to the idea that it seems to have had a positive effect. According to the instruction booklet, it protects against ticks & fleas and lasts up to 2 years.