One thing that always surprises me is how many times companies reinvent the wheel and the need for it. In your post you mention an expenses system; something pretty much every company will have to implement. Since HMRC require this information you'd think they'd provide a tool that everyone could "plug into", giving them full visibility of the data they require in a standard format with little effort, and allowing businesses to also benefit by just downloading the relevant information from this service into their own systems for any internal needs. If all companies were using the same service this would also be one less thing for new employees to learn, since they'd be familiar with the expenses process from previous jobs.
On a persona note, I'm definitely in the automater category; on the few occasions when I've left a task unautomated because it was only supposed to be a one off it's come back to bite me repeatedly when month after month that same one off task pops up (admittedly after 2-3 repeats I then ignore the advise that it's a one off and automate anyway). These days if I can automate a task in slightly over the time it would take to perform that task, I automate by default. If there's a significant difference I weigh up the likelihood of repetition (by myself and/or others) against the extra time required to automate it.