It doesn't take very long to get to a point where you can benefit from adding weight to chin-ups/dips. Someone able to do just 1 chin-up at the start of lockdow

It doesn't take very long to get to a point where you can benefit from adding weight to chin-ups/dips. Someone able to do just 1 chin-up at the start of lockdown could have made some very good progress now depending on how well they trained, their physical proportions, and athletic history. Also, some people simply benefit from exercise variety. I personally get sick of certain movements after months of doing them and need to switch them up purely for mental motivation. Another issue with bodyweight training compared to free weights is training legs and hips effectively. Plenty people will be able to add resistance right away to something like a squat.