Why Not Texts?I don't mind brief texts to say you're on your way or similar, but when I respond to requests for advice, provide quotations, or report on the condition of your equipment, it's very different.
The prime need here is for me to distill everything I know about your situation down to what you need to know to make an informed decision, and try to lay that out clearly, possibly to someone who has limited technical knowledge.
CompositionWhile the aim is always to provide a simple, clear answer, reality does get in the way. There may well be "ifs" & "buts" involved, particularly if I have scant information to work with. This can mean quite a bit of editing, which can take a while in the best of circumstances, but is an absolute nightmare on a phone.
ShorthandReceiving text shorthand can be ambiguous or confusing, particularly with people you don't already know.
Communication HistoryI've usually got a number of technical conversations going on at any time, so need to be able to refer back easily to everything from the PCs.