I can't see the liability issue, they are not that concerned when it comes to the few 100 people that die every year while using their phone in the car.
BTW, you can get i.e. uTorrent from the official Play Store. Actually the only time I did use was on holiday when I d/l an episode from a TV series - totally legal! Otherwise I don't watch movies on my phone.
But I give you another issue that sux about the Apple system: The country restrictions for apps. And I give an example:
A while ago I was in Germany, and Germany has a great cheap supermarket - ALDI. They have an app, but I can't get it because I had no access to the German iTunes. It's a free app too.
What are you going to do with an ALDI app outside of Germany? Browse there assortment from afar? The different regional stores exist primarily because of media rights that need to be adhered to according to agreements Apple has with its media partners, which is a big part of its business model as explained earlier. If that isn't for you, then by all means...MOST apps and games are available worldwide. Those that deal with restricted media rights content usually are restricted to their home country's App Store. An app like ALDI Germany (Aldi is also in the US, UK, and other countries as well, BTW) probably made a conscious choice to phblish their German app only on the German app store, because, yes, developers can do that. In this case, it is the developer who has chosen to limit the app's availability.
As far as liability I don't mean general liability, I mean the almost certainty that there exists an agreement with media rights holders that the ability to circumvent official sales channels is actively restricted. It makes sense.