Check axle fluid every 7.5K miles?

The owners manual of my 2WD 03 Yukon has checking the axle fluid every 7500 miles. (Axle fluid and rotate tires every 7.5K mi, air and fuel filter every 30K). Checking axle fluid seems a bit silly and unnecessary but usually the maintenance schedules have a reason for listing such things. Anyone have any knowledge as to why checking the axle fluid is deemed so important to list it?

i check mine every 10000 miles. and here recently i have been a little low. so replaced it it volvoline 75-90 synth. dont know why it ran a little low. i have no leaks..

The friction caused by the ring and pinion and all the moving parts cause heat, which breaks down the fluid, just like oil in an engine or trans fluid in the transmission. Once the fluid starts to deteriorate, it can no longer protect the parts as well as it used to, causing premature wear if not changed under recommended intervals. Checking to make sure it is at the proper level is crucial also.