Email was slow and the signal to noise ratio was off, while other chat systems I had used before at work either didn't preserve state, so whatever conversation happened while you were offline didn't get pushed to you, or they didn't scale up to large conversations well. I was constantly talking about the work, planning the work, discussing the requirements of the work, and then in a truly Sisyphean twist, linking new people to old conversations where we had already discussed the work to get them up to speed on our conversation. So, you had your most productive people spending their days explaining why they weren't going to answer questions they already knew the answer to, unless they absolutely had to.