This is because the remoteness means you’re further away from any infrastructure that provides an internet connection.
The same reason you lose cell phone coverage in the wilderness is why you struggle to get cellular broadband like 3G and 4G.
Vast farmlands, trees, mountains, streams, and rivers all make it difficult to roll out infrastructure and also play a role in interfering with wireless signals.
Imagine you’re in a major city with good internet; you can still find it hard to connect to your router when your device isn’t close to it. Similarly, if your device is far away from a cellular tower, it isn’t going to be able to connect.
So, again, go with satellite or fixed wireless if you want the best internet options for rural areas, especially if no cabling or phone line is available.