Let me give you some context how Datapoint came to play and how it was used (at least from my experience):
Datapoint was mainly aiming to be used as cheap data entry systems, take a 2200, attach a few terminals, run data entry software, write a tape and carry it off to your mainframe.
Personally, I started with DP in late 1978 (me being 18 and knowing nothing about IT), the IT team was mostly mainframe educated, meaning could not think beyond 80 character file records (aka punch card). DP had some advantages, like record size limited by disk space only, pretty good ISAM, later very good AIMDEX. Databus as a language was easy and able to be used for processing business applications. I was later working for DP itself, and most of my customers ran business applications, written in house. Later I worked for a software house doing land- and airfreight software, also written in DATABUS and being very successful.
Nearly every company had their own dev people, so most software was custom built. Yes, you shared code between companies on good will (security was not that much of a topic). In my role, we used DP for processing the ordering system, warehouse analysis, banking applications etc. We still used a /360 for some other stuff.
To take away all romance: These were not the good old times. Software was buggy ,hardware failed often. I spent countless weekends, New Years Eve's and christmas days working around issues, repairing disks, salvaging data etc.
ARCnet really became prominent in later years, I believe around 1981/82. I used it mainly in a dev environment. Why? When the DP2200 was in DATASHARE mode, driving terminals, the console was occupied, no editing, no compiling. One had to "ROLLOUT" of DATASHARE which meant all terminals were suspended. This is why networking was important, the main computer was running terminals and you had cheaper computers like a 1500/1800 (not sure about the models) or later the 8000 series to edit and compile. Until then, I had written my own text editor so it could run under DATASHARE, leaving the compilation for night time.
There was also a WAN Arcnet thing, but I cannot remember details.
