More like it needs to exist for THE RESULTS OF YOUR EXPERIMENT to make sense. Not the universe.
Dark matter is what you call whatever is left over when your instruments are telling you there is more something there, but it's impossible to measure any of the something using the methods we have now.
Nobody is saying to you "dark matter must exist for the universe as I understand it to exist"
They are saying to you "if the universe exists as we understand it, there is something more here that we do not understand"