There are probably a number of reasons this was not supported in Maemo - power savings, simplicity, and reliability come to mind. Power savings is obvious, without an active cellular data connection the cellular radio will not be active as often. Having multiple interfaces to the same network (or the internet) is not a simple setup, and requires more complex policy based routing to route traffic back out the correct interface. Without PBR, all traffic would go out one interface (regardless of where it came in), causing many potential issues - including, but definitely not limited to: traffic with an IP from network A originating on network B being dropped (most sane network admins drop all egress traffic not sourced from their IP blocks) and forward traffic routing differently than return (resulting in odd latency/jitter/throughput issues). And then there are application level issues - How should the best interface be selected? What makes the decision (TCP stack or application)? What factors are taken into consideration? What about existing connections when a new network connection is created? What happens when a network connection is lost? It would definitely be nice to see added in the future (fixed in MeeGo?), but only if it can be properly executed.