What is the point of 4G on something that is designed to limit Internet access?

Probably to be able to connect at all, even if only for messaging, email, and phone calls. Hey, it's a mobile network terminal, you've got to have some network access there!

They are retiring 3G like mad, and even 2G towers are getting fewer and farther between (although it's likely that 2G/GPRS/EDGE will never truly go down).

My dumbphone as 4G. Is the way I use to have internet at home. But there are not applications compatible with the operating system (WebOS)

2G and 3G networks will eventually be shut down, so 4G support is part of future-proofing the product.