Why sync to the desktop? Why not mobile only?

When discussing the issue of mobile-desktop-Internet sync with people, one question gets asked frequently:  Why involve the PC at all?  Why not have the mobile device access the Internet directly?  After all, every modern mobile phone has, by definition, a data connection back to a carrier network, over which various services already operate.  Network operators are enthusiastic to sell data services over that pipe, and many users would rather not be bothered with setting up PC software if they can avoid it.

Well, carrier data services certainly have their place, but there are still many situations where user needs are not well served by a mobile-only connectivity solution.  Here are some of the reasons why:

• Network Performance: Even with 3G, both bandwidth and latency over cellular connections are much worse than via WiFi or USB.  Local connections between a phone and a PC in the same room are typically 10-1000 times faster than the cellular connection.
• Costs and Billing Uncertainty: Costs for cellular data can be quite high, and many users remain nervous and uncertain over data access will cost.  Flat rate data plans redress this partially, but they are not available in many parts of the world, and they typically still come with (sometimes undisclosed) usage caps.
• Security and Privacy: There are valid concerns over security and privacy when transferring personal data, and mobile phones hold some of the most private data there is.  Corporate environments, especially, have a need for verifiably secure data transport, storage and backup.
• Operator Control and Restriction: In the past, certain over-the-air services have been blocked when they interfere with an operator’s own for-pay services.  By using local connections, this is no longer a factor.
• Customization and Configurability: Above all, a sync solution needs to fit into an individual user’s workflow.  A local sync application can provide direct access to applications and data on the desktop as well as be more configurable and debuggable.

As someone who not only consumes a lot of big media files on the phone and lives in country without flat rate data plans, but also has strong preferences for how my various apps work together, I find it quite easy to come up with this list.  But I think a lot of people with different priorities and different applications in mind won’t be quite as compelled by these reasons.  I’d be very interested in hearing other points of view, so please post your comments below!