When I bird, I always record everything that I am able to identify definitively.
I then always enter my data into eBird. eBird encourages users to report all species they were able to identify, and marks these as “complete checklists”.
iNaturalist is very different and it seems less oriented towards birding specifically. I personally think that iNaturalist is a little better for plant and insect reports than bird reports, as eBird already handles these very thoroughly. So I haven’t felt as motivated to report birds on iNaturalist. The time it would take to enter a complete bird checklist into iNaturalist would be exhausting. When I bird, I may see 20-30 species or even as many as 50 on some sites at some times of year.
If I saw a compelling reason and benefit to reporting bird observations on iNaturalist in addition to eBird, I might start doing more of it. For something like a robin though, there are already going to be a ton of reports on iNaturalist.
Once I saw a very rare bird, a tropical kingbird, in Philadelphia; it was the first state record in PA and I got a half-decent photograph (a better photographer returned and got some much better photos later and also heard it vocalize.) In a case like that, I would probably also upload the observation to iNaturalist becuase it seemed notable.
Dozens of robin observations don’t as much. It certainly doesn’t hurt to report them repeatedly…but I have better things to do with my time!