I am a TRS with only three gigs, so I am one of the people you are talking about. I had only one gig for the first two years of my Fiverr career. Then I decided to create two more as I was always asked if I provided those services.
I am offering these services simply because it is what I want to offer on Fiverr. I could also offer writing, game development, business plans, video editing, or marketing via YouTube as I am skilled in those areas. Some even more so than I am in translation. However, these things I have no interest in offering here on Fiverr. For me, these are strictly skills I wish to use to expand my own personal ventures.
Also, my current gigs are already taking up a lot of hours every week. I am not sure I would have time to eat if I started offering more things.
Finally, I agree with @looseink - there is no need to fill your gig quota with a lot of filler gigs just because you can. You have to be able to deliver professional quality.
You start with zero gigs. So, logically, the question isn’t whether there are benefits to having less gigs, but whether there are benefits to having more gigs.
This will depend on your niche, your goals, your personal preferences. You’ll find successful sellers with few or even just one gig, and such who use pretty much all or all their slots.
The sensible thing from my point of view is to create as many gigs as makes sense to offer what you want to offer - always keeping in mind that Fiverr doesn’t want “duplicate” gigs - at any given point, and to re-evaluate as you go and adapt your gig situation (create a new one, delete an obsolete one, edit an old one (again, keep the rules in mind; giving your gig a new fresh appearance, changing the package structure of what you offer, etc., is fine, but don’t change a gig in a way that your permanent gig URL and the changed gig title, etc., don’t match anymore)).