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.
Everything has advantages and disadvantages, each of which I think, those who do not have a private key / pharse backup you can contact support to restore your account
And what you hold a private key / backup pharse usually doesn't have support services, so if you lose your private key your money just goes away
For example I lost my bitcoin to xapo wallet since 2018 and they denied me of my coins after sending them mails.
I used XAPO when I was released and never encountered any problems, make sure you provide the correct data so that they can easily help you