The whole point of no-dm, IMO, is that it adds uncertainty to the game, "Did I get him??", in other words you dont know if its clear or not.
Sure you can check the scoreboard, but unless you check it all the time, it can be hard to keep track, since kill and cap points are counted as one etc..
In other words, I think it adds to the realism feeling because I, like many others dont confirm kills with the scoreboard simply because its not that reliable/easy to remember all the time. like some kills are just obvious, you meet someone in CQC and nobody else is around, no point in checking.. you help a cap, no point in checking, then, you think you got someone up on that roof, bring up the scoreboard and it just says "12", ok, did you have 10, 11 or 12 before that kill?