If you can get onto Offense it's absolutely not bad to finish, however not everyone has a lot of time. Some people may only be able to play 2 hours a day for example. and with the chances being 50/50 getting on offense, they could lose out on daily/weekly challenges. A challenge should be possible on both sides, not just one. Like I mentioned, when I queued for Rush and Breakthrough, I got one offense in 10 matches. So if I were only able to play for an hour, I probably never would have gotten that offense game. I could have just left the game if I got onto Defense, but that should not be the ideal way to be able to accomplish these challenges.