Lordy
My son has two travel cards attached to his Swiss pass and we do this to prove to non SBB scanning companies that he has a disabled travel card and as such it entitles one of us to travel for free. Without having linked it to the Swiss pass on the app it would be impossible for most private companies to have any idea what was on the card.
Disabled passengers used to have a distinctive green Ausweis and there has been a lot of complaints about how other companies who would happily honour the card are unable to scan the card to know if you are telling the truth or not. The linking it to Swisspass in your app is the only workaround we have found.
For parents like us who have an older child who cannot manage to have his own phone, we use two SBB apps side by side on our own phone - we use SBB traditional for my GA and we use SBB Preview logged into our son's account so we always have a digital record of his disabled card.
To me, the best change they have made lately is the "shopping basket"function, allowing you to buy multiple items (eg bicycle ticket, reservation, etc) in a single transaction. Previously you were forced to make multiple single transactions.