It saves you from having to type
Ooooh my poor fingers.... yes, I used to worry about abbreviating everything as short as possible, and I still control my loops with i j and k, but when it comes to ambiguous var vs QString or int32 or float or double or whatever type du jour is, I'll take the time and effort to write it out rather than taking the time later to untangle how the ambiguity might have resolved and all the unexpected things that might happen as a result of an unexpected resolution.
Back in the day, I was getting a new "99% compatible" DOS version every 6 months (until we transitioned to the PharLap 32 bit extender, got more memory to work with AND stopped the perpetual upgrade treadmill.)
That "99% compatible" thing means: in a 10,000 LOC codebase, you've got 100 things to fix before it works on the new DOS.
I really liked working with Qt from 2006-2024 or so, the only major break was 4-5 (must admit, I never migrated to 6, and nobody forced me to...) and the migration from 4-5 was less painful than a DOS version bump. Also, Qt fully insulated our code from garbage changes happening at lower layers.