If you are in service industry then there's no other option for you but to respond on time. I know I would not sound wise when I say that. But such small and petty things are tossed big time in some organizations. It is really difficult for me to fathom 'why people do that?'
If you are not equipped with information as to what needs to be responded to client or any other stakeholder then I can probably understand. However, when you have everything that is required to notify the other person and yet you don't do that then it raises a question on your ability to work in professional setup and sensitivity towards other people who are waiting for your response.
I remember one such incidence when one of the department was expected to respond to some client query. The function got this update on day 0. The news got circulated to concerned people internally on day 1. The required information and the solution was provided back to the team with all other required explanation on same day i.e. day 1. Nothing happened on day 2. The person who should have sent the information on day 1 offloaded the responsibility of response to somebody else on day 3. And I really don't know when client actually received the information.
Such things would pose a great difficult for the growth of the organization. And organization that will work on such small and little human things will succeed for sure.