I have played live cash games where we were all talking and having fun. The dealer was laughing because we had an hour that only 5 hands were played. That said, online times are not that slow, just we are stuck looking at a screen, so it seems like it is slow. Some people are more analytical than others. The person could think slower or is considering all possibilities. This is not slow if they are only taking 15 seconds. Now, if they keep dipping into the time bank, well, they could be attempting to put others on tilt to make their game easier.