Because there's no point. We visit 'popular systems' to perform a particular task. Time wasting mupppets are time wasting muppets delaying performance of initial task. Solo/Mobius/Block when visiting 'popular systems' = time saved. Kinda like asking why take a detour through the backroads instead of sitting in stationary traffic...
Well… I must say, I find this approach amusing and representing, much more so than the so called 'gankers', the most counterproductive thrust to the overall dynamics of a game and a shared ecosystem such as that of Elite's. I also see now that there's no sense in trying to argue for any creative solutions as these same conversations have been had years ago when I could not, for the life of me, understand how people value min maxing of some make-believe cargo over actually interesting interactions. This goes way beyond just the matter of gankers and, contrary to what many say, all this blocking and going solo affects others too, changing the overall dynamic of the gameworld for everyone.
It is, at the heart, the same kind of rationale as one employed by several western governments in recent years in their attempts to enforce equality and moral behaviour, namely enforcing or prohibiting use of certain words in the language to counter bullying or discrimination. The problem is there's no way you can clearly determine and demarcate who's ganking from who's roleplaying and ganking just a little bit from who's just roleplaying as a pirate or whatever else. So, you end up with an infinitely stretching granularity of the category and suddenly everyone who killed someone is a ganker, ruining games for others.
So, while I myself love to roleplay and immerse myself subsisting as petty criminal and gun for hire, poaching some lonely miners or traders here and there for a few canisters of cargo, without killing them, and constantly on an edge of bankruptcy, I have already encountered several players in the open who'd not want to engage in any form of communication or interaction whatsoever or go as far as to actually, physically disconnect on contact. Because they are already conditioned into thinking that you may as well just not go Open because everyone there is a trying to make you miserable.
This breaks my heart a little, really makes me sad. Because it leaves me with an overwhelming feeling that most players - people, to use a broader category - truly lack imagination, and, instead of changing those things which are in their power to change, to dance around the experience that comes at them effortlessly and playfully, try to change that which they cannot and end up with a dynamic where everyone is too scared to engage with anything.
What's true in the real world, remains true in the simulation. Elite Children's Birthday Party indeed.