When do you use amortized time complexity and when to use unamortized?
You can find the motivation for the amortized analysis from this reference:

The motivation for amortized analysis is that looking at the worst-case time per operation can be too
pessimistic if the only way to produce an expensive operation is to &quot;set it up&quot; with a large number
of cheap operations beforehand.

Hence, unamortized (asymptotic) analysis means considering time complexity of an algorithm (instead of each operation) when each operation can be counted in constant time.