Or as a second "city car".
Not everyone is keen to navigate through clogged cities, narrow Sois and parking garages with a bulky truck.
For me it looks as a budget decision only.
Celerio is targeting the bottom of the low budgets.
Even comes with a manual gear option. 3 cylinder, 68 HP.
Swift is 200k to 300k above Celerio (close to double at the top).
CVT automatic like most. 4 cylinder, 83 HP.
So if one likes such a compact thing and budget is not the priority the Swift is of course preferred.