As a counter point, I was almost fired for not choosing to build a SPA for an internal app which was going to be used by 3-5 people, 5-10 times a month, if that many.
I worked at large accounting software provider, and internal billing system used static pricing which was changed once a year. The company wanted to move to a more flexible system where pricing can be setup based on few rules like customer type. For this the ui and backend system needed to be developed. Design I proposed was a single "monolithic" service which did everything including UI and UI was supposed to be a old style mustache templates and some minor jquery. Instead they went with pub-sub systems, 4 different microservices, a react based UI, api which used json-schema, even to send data back to UI. When I left a team of 6-7 people was working full time on this and they were about 20% done.
I worked at large accounting software provider, and internal billing system used static pricing which was changed once a year. The company wanted to move to a more flexible system where pricing can be setup based on few rules like customer type. For this the ui and backend system needed to be developed. Design I proposed was a single "monolithic" service which did everything including UI and UI was supposed to be a old style mustache templates and some minor jquery. Instead they went with pub-sub systems, 4 different microservices, a react based UI, api which used json-schema, even to send data back to UI. When I left a team of 6-7 people was working full time on this and they were about 20% done.