Scrolling in chat is slow to load messages
Scrolling through past messages in chat or search is too slow to be useful to do on big threads. Often instead of searching for what someone said yesterday, people just ask again because it is so annoying. It defeats the propose of communicating well the first time, because you will be asked again anyway.
Derek Thrasher commented
Sean Ellis commented
The amount of storage required to cache conversations would be small compared to modern disk sizes. All messages should be cached locally for speed, although there should also be a setting to configure maximum local cache size.