It is because without vector spaces, you could not do linear algebra, which you need for everything. Without categories, you cannot do category theory, which you need for ... what exactly?
That is the point here.
> CT is applied to many domains.
Yes, but in which of those does it massively help? I just looked up ZX calculus, and I am sure you can formulate that better by not mentioning CT at all.
Based on what? Sorry, but what you're saying is beyond arrogant (considering you have zero knowledge of the subject).