Jenkins benefits even if you are not using a CI process,

Having the collective results in one place has a lot of advantages

Can get results from different tools (might be using separate ones for UI, API and unit level) in one place

Even for one tool, having all parallel runs in one place is a big blessing

Secondly can have a combined history of all the results (in Junit format used by Jenkins by default)

Thirdly, it allows for parallelization to your tests

To scale your automation, this is going to be a must

Number Four: One can centrally control the automation execution resources from one place

Having parameterization will make things even more easier