Most modules have some feature or other that needs to communicate with infotainment or another module that needs to communicate with infotainment. Error reporting is the big one, but there's lots of little ones too. The brake module, for example, may be involved in tire pressure sensing, and also takes configuration for traction control and reports activation.

It's hard to find an appropriate segmentation for an air gap without sacrificing features, and most customers won't trade features for "security".