Consider how difficult it would be to run an interstellar terrorist organisation.
This is one of the reasons why I've always found the Ine Givar to be vaguely ridiculous. They're basically a response to the real-world. Terrorism is (and has been) a hot topic of conflict in our world for a few decades now, so writers of Traveller have tried including it into the Travellerverse. I pretty much believe the Ine Givar sounds good if you don't think too hard about it (something in common with a lot of the 3I). Once you do...
To me, the evolution of the 3I lore involves a kind of "philosophical shrinking" of the Imperium for no other reason that I can fathom than the limited imaginations of the writers involved in Traveller itself trying to fit the Imperium into model of a Earth nation-state. When I say "philosophical shrinking" I overlap with a lot of users on here who talk about the "monolithic nation-state Imperium."
Early versions of Traveller involved a loose Imperium (before some grognard steps in, yes I know, the earliest versions of Traveller didn't have an Imperium at all). However, in the beginning the 3I was an "Imperium that ruled the space between worlds, not the worlds themselves." Ever since then there's been a kind of "power creep" of the Imperium; it seems to get more and more powerful, more and more invasive into the affairs of individual worlds, and even the lives of those living on each world. Eventually we had this concept of Imperial nobles that somehow "rule" over worlds (wait, what ever happened to not ruling worlds directly?), "Imperial worlds", "Imperial culture" vague ideas of the Imperium taxing individual citizens, a common physical currency, an "Imperial Army", megacorporations with Imperium-spanning operations, and finally interstellar banking with a high level of liquidity in markets spanning lightyears that much of this would require.
I call this a philosophical shrinking because the basic tenet of the Imperium that should have precluded this monolithic Imperium has never changed - communications is limited to Jump. A Jump takes one week, so getting information between worlds is at least a one week process, often much, much longer. How many of these concepts of this "galactic village" Imperium could work in a situation where communications are so slow stretch and finally break disbelief for me.
This is a roundabout way of saying that I don't think the Ine Givar would exist unless we've gone pretty far down the "Monolithic Imperium" model.
Terrorism is a kind of warfare that appears in response to specific situation - the opposition's power is so overwhelming and pervasive, only token and often symbolic strikes are possible. If the opposition's strength isn't that great, then guerilla warfare is more common. If the opposition is weaker still, then outright warfare occurs.
In more loose versions of the Imperium, there's simply not enough Imperial interference to really get people resentful of the Imperium. If they do somehow get resentful enough, in looser versions of the Imperium, the Imperium is going to have a lot more to deal with than a few people planting bombs; the Ine Givar should be able to organize and arm sufficiently in a looser Imperium so that it is fighting guerilla wars to making actual strikes on the downports or highports on worlds.
I have doubts if the actual logistics of Jump-speed communications make the monolithic Imperium models even possible - the kind that would have a tight enough grip to make resistance to it only possible based on modern terrorist models and where somehow the Ine Givar is a terrorist organization that pops up in some form across multiple worlds.
