I've only played at home and everyone announces the tiles (so an interruption every 5 seconds) so maybe that's the problem. Maybe if you're good enough at it you can do the game on autopilot while chatting? I'm always slowest even to stack the tiles at the start and that's without distractions!
I have been lead to belive that community Mahjong is an excellent time for catching up, but then again, I've never gone and don't know how to play.