Here's how Bungie framed Story Strikes for Curse of Osiris: (Destiny)

by Pyromancy , discovering fire every week, Friday, January 05, 2018, 20:30 (2354 days ago) @ CruelLEGACEY

That’s because they were just story missions that got reused as Strikes. It was a lazy trick and it doesn’t work well at all. You don’t realize you “just played a strike” when you first go through them because they’re labeled as story missions and you go through them Solo. Why would it ever occur to anyone to think “hey, did I just play a Strike?”

Then, when you jump into the strike playlist, you get Osiris saying “oh, hey... that thing you already did? Yeah, I need you to do it again... for science...” and then you play through the exact same mission, but with 2 other guardians along for the ride.

I’m sorry, that is not good narrative integration. That is lazy re-use of content with barely any attempt to disguise the fact that Bungie was willfully misleading with their advertising of CoO. You (Bungie... not YOU, Raga) don’t get to say “X new story missions and Y new strikes” when the missions and strikes ARE THE SAME MISSIONS. I’ve had plenty of criticisms of Destiny over the years, but this is the closest I’ve ever come to being legitimately angry at Bungie, because at this point they’re just being insulting. No, Bungie... you actually cant just copy and paste the same missions into different activities and try to pass it off as more new content. It’s total BS.

I don't necessarily disagree totally with anything you are saying. And I don't necessarily agree totally with how Bungie framed them up, but here is how Bungie framed up Story Strikes for Curse of Osiris, in their own words:

https://www.twitch.tv/videos/203198197?t=35m47s
Curse of Osiris Reveal #2 – November 21st, 2017
Participants:
Deej: King of Awesome
Dan Miller: Game Director - Curse of Osiris
Dave Matthews: Art Director - Curse of Osiris

(I'm not attempting to mis-quote anybody. I transcribed and left out some un-necessary face to face conversational cues, tones, and mannerisms so that it would flow better by text)

Timestamp ~ 36:47
Deej: “...So as I enjoy the campaign, If I’m a solo player who enjoys experiencing a campaign all by myself I don’t need to trouble with other people, I don’t need to worry about someone going away from their controller and not participating. I can enjoy that Strike all by myself as a lone gun man. And then later on, let’s say I experience that Strike as a matchmade activity, then it will be scaled to accommodate the cooperative experience? Is that what you are telling me?

D Miller: Yes, Yeah,

Deej: And uh, am I going to feel like I’ve been deprived of 2 additional story missions?

Dave Matthews: Not at all. No. I think one of the great things about this is that every Strike has always had a story that it told. And by bringing those and making those part of Osiris’s story allows us to, I think, enrichen the overall narrative that is Osiris’s history and everything we want to talk about.

Deej: Give people more a sense of context of those Strikes. They’ve always felt slightly separate from the other story that was told, like you’ve finished your campaign now go back in and fight some other additional bosses or something like that.

D Miller: And when you buy the expansion, it’s really nice, because you can immediately see and play through these experiences without having to do the random Matchmaking thing . And you’ll right away get to see: “oh, these are the Strikes that come with it”, and then later on as you’re playing the matchmaking they will be there as well.

…

Deej: … wanted to give people a sense of how Destiny 2 would be changing. You know some of the different new ways to play. While story Strikes are a step in that direction we are not going to play one today, we are going to save that for players to experience as part of the campaign in the Curse of Osiris Campaign.

Dave Matthews: In 2 weeks!

Deej: In 2 weeks

In a way, part of the reasoning for Story Strikes seems to be sort of an anti-griefing methodology?
Personally, I do have to say I enjoyed being able to play the Strikes for the first time at my own pace, without having random player 'XxXxBroFacexXxX' sprinting through the thing at drunken speed-run pace teleporting me through the checkpoints missing the story elements.
Over the years, this has been a complaint by some regarding matchmade Strikes.
It was also nice not having to worry about freeloaders or AFK'ers not pulling their weight in the fight.