Why is WhatsApp using my iPhone storage instead of iCloud?

On my Iphone storage, whatsapp is taking up 62.6GB, in my iCloud storage whatsapp is taking up 42.6GB. I have an abundant amount of icloud storage, so why is whatsapp backing up onto my device storage and not icloud? This is quite annoying as it’s taking up too much room on my device storage even though I have plenty of cloud storage available. I’ve tried everything, and tried looking everywhere but I can’t seem to find this issue elsewhere, I’ve even tried to play around in the app settings and on the settings on my phone, does anyone know?

[Re-Titled by Moderator]

Original Title: WhatsApp storage on device vs iCloud