As members pickup more cameras for their home setups.. it starts to add up, especially with those nice PoE+ PTZ cameras we all want to deploy..... ;-)
So PoE switches have power limits, and there will be loss of power on the cables, and while each individual camera does not consume a lot of power it does add up - and ideally you do want to have the equipment be reliable - thus lower power use = lower heat = in theory more reliable. Also we do need to do power calculations to ensure which ever PoE switch ( or NVR w/PoE ports ) can handle the cameras and other POE devices attached to the switch.
Yes, probably less of an issue for most home users - and certainly a greater issue for a large setup. ( example companies with a lot of POE equipment - like phones, as the switches are often in datacenter areas which are climate controlled - so more power consumed, higher heat generated - more AC costs )