"Original" equipment vs. upgraded equipment

Hi,

I've always been curious as to why this is so important...at least to some folks? I've even seen one ad that stated: "born that way and not an upgrade". (Give me break.) As long as the equipment was upgraded by the OEM and brought up to current specs, what difference would it make, sonically or otherwise? Do people really believe that an upgraded piece of equipment is somehow inferior to a non upgraded piece? Can you hear a difference? Will it not last as long?  Please do tell. Thanks.