Most people focus on bandwidth when they think about internet connections, but speed is only one metric for measuring internet performance. Often it's not even the right one. For example, for real-time applications such as voice and video calling, what matters most is reliability. VoIP conversations (including Skype, WhatsApp, and Google Hangout voice calls) take up minimal bandwidth - much less than 1Mb - but bandwidth has to be consistent. Even a momentary dip in bandwidth - or a couple of seconds of downtime - can make conversation impossible.
With residential internet technologies, such as cable, DSL, or Fios - even though the physical medium for Fios is fiber, its architecture is effectively still residential-grade - your actual bandwidth is constantly fluctuating and rarely if ever reaches 100% of your advertised bandwidth. It may even drop to zero at points. That's because you are also sharing that bandwidth with your neighbors in your building, and possibly your block.
I've tried to illustrate this with the image below: