This is my honest answer, and just something that I believe, and is no way intended to insult anyone.
No, I don't believe it matters that you, me, or anyone else exist. I've always thought of everything as being in harmony with "the whole". That is to say everything has a supportive role for the existence of something else. Much like all the cells in our bodies.
Humans, however, do not play a supportive role. We are more like cancer. A mass made up of rogue cells that destroys surrounding cells. We do not (as a whole) play any importance on anything else's survival other than our own. Take us out of the equation and The Planet, and all the rest of The Universe, will continue on.
That all being said, I don't know why mosguitos exist either. I mean bats and fish can eat other insects.
Just my opinion.