Software update via wifi or carrier

[SamSungtwo]

My A70 has an option to update via wifi. I have noticed other Samsung devices relying on a carrier to release software. 

Why is there a difference? My Android security patch was received via wifi.

[Fatwa]

the carrier releases the update... the formats the data is transmitted is a separate matter.

Seeing that updates can be large, users typically want to do that via wifi to avoid mobility charges.

Enabling the toggle automatically download to you device via wifi without seeking your permission on each event.

[CHMultimedia]

You'll get the same update no matter if it's via WiFi or by using your mobile data. There's no difference beyond that.

[SamSungtwo]

What is the explanation of people stating they have to wait for their carrier to realise software update, when they can get it directly through wifi?