The default speed limit is set at what it is because currently the physics engine can only handle objects at that speed when they collide, I run a server that sets the max speed to 100, and I get problems with ship collisions not properly being handled. As a result, ships can sometimes phase through one another and become stuck to one another, a small ship could phase into a very large ship and let the user hack internal systems such as main cannons or missiles. On top of this, increased max speed makes a lot of other collisions buggy, an example is ships shaking violently while on a planet if they have turrets attached.
Sure its fun to set the speed limit higher, just remember it comes at a steep price.