Bugs eeewwww!

So this little guy
was hanging out on my window sill today.
It got me thinking
what is his purpose in
life?
What I mean is
why are there insects in the world?
Scientists say they help
pollinate plants or they become
food for larger animals.
But why? Why did insects
have to be created to pollinate
plants? Why can't a plant be created that
can pollinate itself or others?
Why create an animal that exists on a diet of insects?
it just seems redundant.
There's an aphid which is a small insect that feeds
on plants, so a ladybug eats the aphid for food,
so a bird eats the ladybug for food, so a cat eats a bird for food.
On and on it goes. Why even have this chain of food?