Are Our Tires REALLY that sensitive?

I don't know jack stuff about anything other that what I do, or can opine on. My Georgetown tells me I should run my 22.5 Michelins at 95 lbs. So I run my rig at 95-100 lbs. cold. Why do I need to weight my rig and how many really do? Or worry if two bikes that weight what, 40 lbs., will make a difference! I do agree (in theory because I know nothing) that folks RV'ing in the Southwest especially will have a whole different set of circumstances to deal with when you have air temps over 100 degrees days on end and only imagining what the road temps must be some days. An acquaintance of mine has a 1988 Winnebago with the original tires! I asked Gene, who for fun races sprint cars and is maybe the best mechanic I know how could he feel safe driving the Winnie. He just told me that they weren't cracked or dry rotted, he keeps them inflated to recommended pressure even while stored over the winter. In 2003 I bought a 1977 Kawasaki motorcycle from a friend with 3600 original miles on it. I was amazed that the original 36 yr.old rubber was still on the bike. My friend who is a mechanical engineer told me he stored the bike in a heated garage away from any electrical source, what ever that meant. I drove the bike for another 2000 miles before I noticed they were finally showing signs of cracking and replaced them with new Dunlops.