I can’t believe this is actually a thing. I’ve had nothing but good capture games in Bots Battle. Got Old Man Cranky about eight times now and never lost a match.
I doubt that’s the real reason behind it. Most lores don’t take that long or force you to go out of your way to achieve them. Sure, there are some, but I wouldn’t try to go for Killing on Rails in a Capture Game either way.
What @Lehonay wrote about the Titles is closer to the truth. Certain Titles (BBB, WoS, Coopetition, Right Behind You) are almost unobtainable in Capture. If people try to go for these in a Capture Game, it can have a negative impact on your overall team performance.
If you see your teammates trying to go for one of these titles, just advise them to do that in Incursion (where the odds are much better).
Last but not least, I found it helpful to use a character with good roaming capabilities (like S&A), when I’m not sure what to expect from my team. It adds well to the team, regardless of team comp.