Or does everyone have to have speakers turned up to hear a phone call without headphones?
How does this work in an office with people sitting near each other?
Using a soft phone requires speakers and microphone, implemented by either a headset or PC speakers and mic.
It can be disruptive to nearby coworkers if the user isn't using a headset, however using speakers and a microphone would essentially give you a speaker phone, which could be useful in a conference room scenario.