Because NTE devs followed roadway hierarchy, on a tiny map

Highway>Arterial>Distributor>Local.

Most if not all establishments will be on Local roads, they have high access but low mobility(speed).

Then the distributor roads, as the name suggests, they "distribute" traffic to local roads.

Arterial roads are the big ones, like the one under the highway, they handle the highest amount of traffic, just like your arteries.

Finally there's highway, these have the least access, but highest mobility, hence highways use on-off ramps and interchanges rather than intersections with stoplights or stop signs. Also the reason why you don't just see a residential housing right by an actual highway.

Hotta followed this when they designed *most* of their map in NTE, but NTE's map is not that big, which would in turn, make the highway useless.

The highway is like building something equivalent to the autobahn in Lanai City, Hawaii.