Its nothing to do with quality but rather the agreement with Telstra
If there is an agreement with Telstra they're doing you a favour IMO. Much better to watch the whole picture than miss out on a third of it.
This is all about aspect ratios.
The football is filmed in a ratio of 16:9
Most tablets ( especially iPads) are in a ratio of 4:3 in landscape .
You can't make a 16:9 image fit a 4:3 ratio without losing some of the picture.
This is the same as the people who complain about 'black bars' when they watch a film on their 16:9 tv that was filmed in a ratio of 2.40:1. This is naturally wider than 16:9 ( close to 1.85:1)
It's like when you're at the cinema at the previews are shown in 16:9 (close to 1.85:1) and then the curtains go wider for the films aspect ratio of 2.40:1 ( not always though , plenty of films are also 1.85:1)