Why? Light travels from Berlin to SF in 30 milliseconds. That is absolute minimum you can do. This is not even roundtrip time.
So when Starlink tells you it will be 20 ms, just think about 20 ms to where? To the nearest satellite? Sure.
These satellites are at an altitude of 560km, so it's not hard to imagine there are some places where it could be faster to use Starlink (say Spain - Turkey). You also need to consider the speed of light in the atmosphere is faster than fibre optic cables by around 40%. However if there is a need for something like that, then it's probably already going via satellite.
For the average consumer these will probably be faster for Western US - EU just because there are less hops and less companies involved (as I understand the backhaul isn't yet going between satellites).
Online gaming is mostly where this matters. I don’t know much about this but I assume most games have geographically diverse set of game servers so no matter where you are (within limits) latency isn’t terrible.