How to correctly describe the work of the client-server architecture?

Question

API

I've been struggling with this issue for a week now and I can't figure it out. The photo shows a client-server architecture diagram describing the pull-to-refresh function. I can't figure out why service1 and service2 are connected in series

Answer 1

For example, service2 is ordering a taxi, and service1 is cartography with building a route from point A to point B, because this is needed to calculate the cost of the trip. Why are these two services not merged into one? For example, because a map service can be used for many other purposes.