Their bandwidth savings is minimal to almost nothing. And internet connections have gotten faster over the past decade or so.
Many people have metered internet connections and this feature can make a very big difference for them. You have the option to disable that plugin if it isn’t useful for you.
OK, but the thing is, the vast majority of updates only include a few Delta RPMs.
I can be downloading 20 package updates and only a few of them are Delta RPMs.
Why aren’t all of them?
And still, a few percentage points of file size is pretty much insignificant.
Part of it depends on how often you update. Delta rpms are only between specific versions and not everything is suitable for a delta rpm. Again, I suggest that if you don’t desire this feature then you just disable the plugin. It is useful for many, but if it’s not for you, then luckily you have an option for your machine to behave the way you would like it to in this case.
OK, so how do I disable it?
In your /etc/dnf/dnf.conf, you can set
deltarpm=0. This can also be specified on a per-repo basis, as well.