I want to start off by saying I dont actually know the answer to your question - but I believe it is because gravity is weird all the way around. It is basical

I want to start off by saying I dont actually know the answer to your question - but I believe it is because gravity is weird all the way around. It is basically imperceptible at the micro level but is dominant at the macro. Its by far weaker than all of the other forces (38 orders of magnitude!). Even at solar system levels, gravity is strong enough to keep the planets in orbit but the solar tide is minimal. My sense is that while dark matter is abundant, even if our solar system was full of it you probably wouldn't notice. I don't think we did notice it until we started to look at things on a galactic scale. (if any of this is wrong, and it very well might be, id love to be corrected)