Bitcoind is not designed for a mobile user:

1. Setup a wallet before starting to sync so that the system can prune the important thing.

2. No need for any of the RPC stuff.

3. No need for the desktop GUI

4. No need for any of the configurations they offer today.

5. All the gossip stuff can be reduced to simply receiving a transaction for 0-conf notifications and not doing anything with it.

6. The node just observes new blocks. It doesn't send anything to anyone else. It doesn't "participate" in the network outside of simple transaction broadcasting.

7. No advanced wallets. No scripts. No multisigs, nothing crazy coming from the phone.

Etc, etc, etc.

All we want is a simple wallet that you can receive and send. It's not a wallet for large funds, just small services. A checking account that is on-chain.