Sure you can, @healthyswimmer! Sure you can, if that is your personal preference. Its all about freedom, freedom of choice 
But this freedom is slowly being restrained all around the world, or never even existed.
You might be in an area where a single telecom provider holds a local monopoly and overcharges you. This is a reason many people started using Whatsapp because its free if you have an internet connection (and many became addicted chatters in the process, joining chat groups, sending funny pics, etc.).
Or you have friends and family living abroad and you want to actually see them, so you use e.g. Whatsapp or Skype video calls. If you have a distributed team of co-workers or remote business relations, seeing peoples expressions and gestures becomes important, so you use video conferencing, maybe with Google Hangouts. Some people want Facebook-like functionality to catch up on their friends’ activities in their own time.
Even your simple telephone example may already use the internet (using voice-over-IP, or VoIP, via your all-in-one internet package).
So then, given your choices, all of the above discussed issues may be at play. Monopolies, personal data collection, non-existing privacy, etc.
The freedom of the internet is under threat. Not only by large corporations, but increasingly by governments, who like it to be fully regulated and under their control. This is not only the case in China and autocracies, even the USA - supposedly the Land of Freedom and Democracy - plays a big role in this, this year alone ditching net neutrality and adopting cleverly disguised restrictive bills like SOSTA/FOSTA (under the guise of protecting sex trafficking, the unclear wording of the bill makes providers responsible for the (mis)behaviour of their users, creating a huge legal minefield).
Decentralization is one of the tools to fight this 