Hello.
This is intentional.
We have an ncurse-libs5 package but we decided to not enable it by default since it is not an ABI we publicly support nor is ncurses used during the upgrade process.
However ncurses can be build with ncurses ABI5 subpackage enabled by building ncurses with --with-ncurses_abi5 passed to rpmbuild/mb2.
On OBS this can be achieved by defining %_with_ncurses_abi5 1
Any program uses Ncurses has to be rebuild with the newer package that provides ABI6 installed.