Lippert Axle Grease?

Question:
Why is it necessary to "recommend[s] an annual bearing removal/cleaning/repacking of the axle bearings" for a trailer that in essence travels probably less than 5000 miles every year on dry, not salty or sandy roads, with a single axle that allows differential individual movement of the wheels and bearings (that is, there is no side to side or angular torque on the bearings when going around a corner) and that weighs less than the tow vehicle that tows it?
The same recommendation is on my 10 year old 5x8 foot utility trailer and was on a 14 foot boat trailer I had. Both never have had new or repacked bearings.
Besides the trailers, I have owned more than 15 vehicles in my life, many with life spans of over 100,000 miles and I think I replaced one wheel bearing and never repacked any of them.
Is this recommendation a question of manufacturing quality differences between cars,trucks and trailer components or is it like changing engine oil every 3000 miles, self protection and collusion?

Thanks for the explanation, Outbound. I do indeed check the hubs on the trailers at a stop. I will follow the manufacturer's recommendation for the RPod greasing and repacking, and, while I have greasy hands, do my utility trailer at the same time, from now on.

Originally posted by Outbound I wish that someone would invent a sealed trailer bearing, perhaps packed with a bit more liquidy grease that would spread around more quickly and thoroughly after the trailer had been sitting idle for a few months... they wouldn't even have to pay me for the idea, just ship me a couple of the completed product.

+1!

How do you check bearing temp during a trip?  Do you have to remove the cap?

I'll have to remember to do that from now on.  I put about 4,000 miles on my pod last year.  Greased the hubs, but didn't clean/repack them.  How difficult is that?  I have the Lippert super hubs.  That sounds like something I'd have the dealer do.