I know HA is another thing, I mentioned it because it was my only other (and short) experience.
I understand your point. In fact, I could dump the data directly to influxdb directly, but then I would not be able to cross the temperature data of UPS and server to control the smart switch powering an extra fan. Also, both APC UPS and IPMI provide air temperature, which saves the money of an extra smart sensor.
See my point? IPMI on its own is a server thing, but it provides useful features also at home, if your server supports it.