I would argue this...
I would agree with you when talking about items that are mechanical with moving parts - you get into wear/tear - failure due to workmanship or stress on the items - excessive use etc.
With all of the tech in these new rigs and all of the computers, sensors, electronics and pc type boards, those will work one day and not the next day. They don't have moving parts and therefore don't care about time.
For the money you pay for one of these - it's a no-brainer to place a service contract on a $75k rig. You can't even replace both headlights for the cost of an 8 year service agreement let alone your PCM or SYNC4 head unit.
15 years ago maybe, not anymore. Besides, it's cancelable if you sell the rig or trade it in. Your "MONEY IN THE BANK" scenario will NEVER accrue enough interest to balance this out.
Just my 2¢