As someone who uses nnn (occasionally lf) all the time, terminal file managers make navigation (especially bookmarking) easier.
Think Nemo’s my default file manager but with GUI file managers I find it hard to switch contexts. I always used to have two splits open with Nemo but if I need to open a new context I’d have to open another instance of Nemo and then I gotta switch between the instances now.
Now, nnn gives me 4 contexts, which can be easily switched between using 1-4. I’ve added zoxide within nnn to pretty much jump to any directory within my system. This isn’t really possible with a GUI file manager. Guess you can add integration to other tools as well to the list of pros of a terminal file manager.
File preview needs a mention as well. It’s easier when you can quickly glance a file and move on instead of opening it.