Matches that are almost over after half a team ragequit from being spawncamped on the first objective are pretty typical of what to expect when you join a match as backfill. So why are players who are forced to sit through that not given some sort of bonus to encourage them to help out instead of just finding a new match?
Currently DB doesn’t reward you at all for being backfill, no credits or mission progress. Hell, it doesn’t even register your existence in the ending leaderboard. So basically it’s just a way to waste a credit booster. But, I’m assuming this is a bug, so I’ll give SD the benefit of the doubt (albeit a pretty major bug that should have been noticed, but oh well).
Even when you ignore the bug though, it’s pretty bad. You’ll almost never topscore when you join a match late, meaning you won’t get the credit bonus for doing so even if you completely turned the match around. This alone is enough of a reason to give players a bonus.
As it is, I usually just leave backfill matches unless it’s early in the match. Maybe I’m a bit of an ass, but being backfill is just annoying, and there’s absolutely no reason to waste your time with it as it is.