What are the benefits of VoLTE/WiFi Calling?

[Winterpeg]

I really have a problem understanding Wi-Fi calling. I have a new Pixel 6a and would like to try this BUT what is the benefit? I am going to be charged anyway for the usage. It makes no cents to me? I use WhatsApp regularly and it works great from anywhere in the world. I know that numbers have to registered for WhatsApp, but some one please explain the benefits of this to me. I am a regular Rogers customer with unlimited calling/texting within Canada and reside for 6 months in the US. If I needed to use my phone regularly, I would just go and get another Sim card down in the US. My Pixel 6a is unlocked. Please explain.

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[MikeJung]

VoLTE gets you better voice quality calls.
& In the US you must have VoLTE on for phone calls & texts; as their 3G networks have shutdown / are shutting down.

VoWiFi is for better coverage when you are indoors.
& It saves battery life.
With Google Pixel-series phones: If you are out & there is an open WiFi network (that you don't have to sign in) it will connect automatically via a Google VPN.
Like at a shopping mall.

Note: When you use VoWiFi, you have to set up a E911 address.
As when you call 911 via VoWiFi, they do NOT know where you are.
& Will receive the address you set up for your WiFi calling E911 address.