In recent years, telephony has been fighting with alternative means of digital communication (e-mail, instant messengers, industrial automation systems) for the role of the key means of communication in any organization and is losing its former position, although it retains one of its key roles.
It is also worth remembering that quality telephony support protects your company from many troubles that can be caused, for example, by hackers. Poor security of office PBX can lead to large losses due to toll fraud. And of course call clarity is important to maintain image of your business. You don't want any "croaking" or "gurgling" to cause any misunderstanding during conversation with your customers!