I always figured that it was dangerous to go to warp inside a solar system if your engines hadn't been balanced. That's what caused the trouble in STIMP.
That's part of it. But DS9: "By Inferno's Light" has Dax object when Kira orders taking the Defiant
to warp inside a solar system, suggesting it's hazardous even for a properly calibrated engine.
I figure going to warp in-system kind of like speeding -- it's something that creates a risk of accidental harm to oneself or others, especially in a region with a lot of traffic, but the risk is justifiable for official vehicles in emergency situations.