As it is, they have the most important systems in the bubble, which makes absolutely no logical sense; No power would allow this.
The problem is, that the measures a power would need to take to prevent them would interfere so much with normal gameplay that it'd be far worse than they are.
For example, take the simple statement "people shouldn't be allowed to blow you up as you're leaving a high-security station". Now think about what actually needs to be done to prevent that, assuming you're flying a ship which can't take much actual fire before exploding.
- waiting until they open fire isn't going to protect you; they can have enough munitions in the air to destroy a weak ship before any of them actually hit (with something heavy enough, they wouldn't even need to open fire, just ram!)
- resettable alt accounts, the rapid ways to obtain cash and materials if time efficiency is all you're after, the lack of need for engineering to destroy a really weak ship quickly, plus inter-player trading mean that any protection can't just be limited to restrictions on "known" accounts - they have to apply to everyone.
- so what's needed is to make sure that they can't get into weapons range of you in the first place
- that's easy enough in theory - just make the no fire zone about twice the current radius and very strictly traffic controlled: any deviation from your assigned flight path is rapidly met with lethal force, and only one ship at a time (other than authority enforcer vessels) is allowed to be taking off or landing at once
- are you willing to take several minutes every time you want to take off or land (unskippable, if you try you're shot down) just to stop people occasionally shooting at you, though?
Sure, the ultra-lax traffic and security enforcement around starports is highly unrealistic, and does allow you to be shot at by other players. On the other hand, when not being shot at, which is most of the time, it's way more fun to be able to boost out of the station, weave past the NPCs waiting to dock, and jump to hyperspace than Queuing And Customs Declarations Simulator 3300 would be.
This is one of the things that bugs me about the game. Interdicting, if you don't have a damn good reason, like a warrant on a pirate (we'll call it a kill mission in the right jurisdiction) should be a crime, or at least a fine. Evading interdiction from a lawful source should at least be a fine.
Interdicting a locally-clean ship
does give you a fine. It'd need to be a bounty offence to give your target the right to pre-emptively open fire on you for it, though, which would have odd interactions with the KWS and bounty hunting (since you can't use the utility scanners in supercruise); you might have a target which it's perfectly legal for you to shoot at in normal space, but it's a crime for you to bring them to normal space in the first place.
In fairness, Elite Dangerous goes very much down the route of "space mercenary power fantasy" where having consequences for your actions would be an inconvenience, so shooting down pirates doesn't even harm your reputation or legal status with the
pirate faction in any way [1]. The response to crimes has to be similarly weak for the same reason - otherwise most Odyssey missions would be permanently making you hostile with half the factions in the system in very short order, and that wouldn't be much fun.
With the gameplay designed around not having consequences for the 99.99% of PvE, there's not really a way to introduce it for PvP without destroying the balance of the PvE game far worse than occasionally being shot at might.
[1] Compare with X4, which is hardly avoiding power fantasy design either, where shooting back at a Syndicate pirate in Argon space is perfectly fine from the Argon point of view - they'll probably help you out! - but it will definitely wreck your reputation with the Syndicate, even though they started it.