Is a VPN necessary ?

If you're not trying to connect to a private network such as your employer, specifically to access resources on that network, not only is it not necessary, it will actually compromise your privacy and security more than it will enhance it.

Public VPNs are nothing more than glorified proxy servers.

A few articles to inform you:

"Don't use VPN services"

https://gist.github.com/joepie91/5a9909939e6ce7d09e29

"How VPN services resell your data"

https://thebestvpn.com/how-free-vpns-sell-your-data/

Some research into one of the VPN providers:

https://news.ycombinator.com/item?id=17258203

Basically a VPN protects your information when you connect to public Wi-Fi networks which aren't encrypted and reveal your footprints to anyone who wants to see them.

VPN is a virtual private network.

It encrypts traffic over a network.

It's only advisable if you do something stupid like connect to wifi hotspot outside of your own house.