> What problem is only solved with reference counting ?
it releases resources ASAP, avoiding random stalls throughout script
thus provides a smoother runtime experience (games come to mind here).
there are algorithms that reduce these stalls
(incremental/generational garbage collection) but, given enough
objects, they will be noticeable again.
Reference counting have stalls problem, too. And not always smoother than gc. For example, releasing a very long linked list.
Reference counting also has issues with circularly-linked objects, which gc manages near-effortlessly.
As always, you must choose the right tool for the job.