They used to be common. Then the forumites compl ained loudly because they always want things made easier. Shrug. Be careful what you wish for.
You misunderstand difficulty with frustration. A very common thing. It's near impossible to fight with a broken canopy, forcing you to run and repair. Yet it's not a "game over" situation, like when your hull reach 0 and you die, which is fair, and depending on how it happen, can make the fight difficult.
On the related subject, here is a very popular and still accurate video on the subject, from Extra Credits. While it's rather old (2013) and some examples are dated or wrong today, the principle is still true. It's rather short and worth a good watch.
Source: https://www.youtube.com/watch?v=ea6UuRTjkKs
To put in context of the video, the canopy breach feels unfair. Even though it's not random, it kinda feel like it, and there are no real ways to mitigate it (outside of "not taking damage" which is a basic rules everyone try to follow). Especially since both the canopy and the guns are directed toward in the front, so if you want to shoot, you need to expose the canopy. There is no "angling" or "armor switching" mechanic, as in world of tank/warship games for the former, or battletech games for the later.
Since it's not really reliant on player skill, it's not difficulty, it's frustration.
Also, NPC don't seems to be affected by the same rule. While the player is basically put out of action by a canopy breach, the NPC aren't. And I don't think they die if their timer goes to 0, like we do. And it's even worse for Thargoids, who loves to breach your canopy, since they don't even have one.
TLDR : unmitigable issue through skill + special rules for player = frustration.
Issue you can overcome through cleverness/skill + NPC following the same rule = difficulty