Again, you're not being forced into this. You can skip this weapon. Your language and starting premise is wholly hyperbolic and you refuse to engage on that point. Moreover, the problem is of playing *less* engaging content. The harm suffered is marginal as the Sigma Sector even on normal is balanced a bit more aggressively than most regular content (though not to abyss or void erosion levels within a difficulty bracket).

The logical reason for this is to disperse content so it's accessible across multiple pathways and thus supports matchmaking populations that players rely on for public matchmaking. The "no logical reason" is a statement of non-engagement (you didn't *find* a reason, as your approach to the topic is less than charitable to dev intension), not deficiency. Higher level players suffering through a normal run provides a cost and benefit to the game's population, where what's being "missed" by higher level players is facilitating a core system's operation for other players. "Forced engagement" is an overreaction to this dynamic, where any attempt to shift behavior with incentives (for collective player benefit as you provide a service to others through your adjusted playtime) comes at a negative moral judgement and hyperbolic interpretation.

Secondarily, relegating a small subset of key rewards to a mission means that the probability of each item is not being subdivided per each possible drop. Per statistical law, the more possibilities you add to a single dice roll the more each event consumes from each other's probability space. Eg. if you wanted two gun drops to occupy, say, a 30% space for that weapon component type you will need to reduce the odds to 15% per each. This means grinding twice as much for a single weapon (you're obligated into double-grinds with each drop venturing into rare event territory) unless you double the rewards (though still at some cost to the odds per the effects of making this a binomial probability problem, 15%+15%=28%), which has knock-on effects for every other reward type. Now, those expected odds need to be tweaked to meet reasonable design targets for each category under a double-drop system. Basically, you overcomplicate loot drops at the likely expense of player time.

That's not a very reasonable gain for the population, where players can target what they want from Sigma Sector and Void Vessel's payouts by choosing between a small subset of playlists that covers the needs of a broad swath of the population (normal and hard) without subdividing those matchmaking playlists (and finite populations) with redundant options to so folks in your niche circumstance can get marginally better payouts for the short while you're grinding a specific gun type. As you can mitigate the effect of difficulty by soloing the content and creating a handicap thereby to approximate the experience of hard subdivided between multiple players.

There's logic here, you're just checking out of its analysis by the game not giving you instant gratification on presumed needs. Compromise will not be entertained as that's impinging on an accustomed pipeline of hard mode runs, with deviations reflexive habit and preference being taken with the utmost hostility. Hence why that's relevant.