GMC still supports my truck.
Sure if you pay them.
Microsoft will support XP if you pay them.
Are factory parts still available for Fords Model T?
When did you buy your truck?
Windows XP was released in 2001, and they supported it until 2014. Computer hardware is generally obsolete in about six-eight years with the current pace of development. So, they supported the product for twice the average lifetime of any hardware that it was sold to operate.
So, does GMC support your truck for twice its average lifetime, free of charge?