Quotes from Bas Aarts

As users of English we often need a grammatical device to make reference to the way a particular event unfolds in time. This is called aspect.

It is because the verb BE has a plain form which does not share its shape with any of the present tense forms that we need to distinguish the plain form as a distinct inflectional form. And if we do so for BE we should do so for all verbs.

Aspect is a grammatical notion, which refers to the way the associated semantic notion of aspectuality is implemented linguistically.