Not all mobile wallets have backup ,just because they are available for your smartphone doesnt mean they are reliable
Do not use mobile wallets with just username and passwords ,they are called online wallets ,they have no backup phrase or private keys.
For example I lost my bitcoin to xapo wallet since 2018 and they denied me of my coins after sending them mails.
I agree, this is an eye opener specially for a lot of newbies who are going to join. Check first if the wallet that you are going to used as mobile apps has some back up phrase or private keys.
Never tried XAPO though, or even blockchain wallet. I only used Electrum and keep by seed and private key safe in case I needed to recover it.