Possibly because it’s a 20 meg download and in-game downloading aborts on a map change, which happens a lot given the short time limits.
IMO the in-game download system is crap - you’d be better off pushing to an HTML redirect where they can grab at their leisure.
Not that I can recall how the ND80 servers are set up, since I didn’t have to download them this way obviously.
To be honest, I’d kill the LMS server (not a game mode many people play), and possibly the SW one too - people like campaigns and XP save 
It’d also mean the people who do try them out will be funnelled to the ‘correct’ mode (objective) - I’ve seen some of you guys on there, but people tend to arse around (knife fights, stacking etc) which is not really what it’s about - I know I just want to ‘play’ the maps as they were intended to be played - nothing else really matters.
Of course, then you might want to get rid of the campaign and just do plain SW mode with XP reset between rounds, but the public just lurves… XP, since they seem to have the opinion that XP somehow relates to skill (when you are a maxxed out medic / engy and can’t be killed, for example - that’s not skill, that’s just patience).
Besides, it’s not a final yet. Also you might well see them start cropping up on clan servers for small practices. The other thing, once these maps are ‘final’, is to approach some of the leagues that run 3 vs 3 competitions - not sure, but clanbase might etc - my knowledge of what’s what in the world of clan play is not great, apart from watching the inevitable formation->folding cycle with the usual scepticism.
Let’s get the maps finished and see where we go from there.
