The Internet (the iPhone automatically capitalized it for me) is kind of like air - it's ubiquitous, and yet we don't see the word air capitalized.
"The bug in the jar is running out of air" c.f. "Don't pollute the air" (i.e., Earth's atmosphere)
There can be (and are) multiple internets. Hundreds, thousands of internets. There is only one Internet. The people who decide the nomenclature of the technology should be the network engineers who have the knowledge to build it. People who argue for "internet" don't seem to understand how internets work.