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.
That is quite unfortunate. Although, i have been in the crypto space for quite some time now and i never knew and cared about this.
Most if the times, we clamour to have mobile wallets, but which sometimes can be used against one.
Some even promise to airdrop and tell you to download their wallets. Out of every 100 persons that download it, 5 of them might be noob and go ahead to store their coins on them.