not 70s but my Mercedes 300TD from 1985 made extensive use of vacuum hoses to power lock doors, run pumps and even to turn off the engine (it's diesel so no spark plugs.) I think it was built that way because electronics were more expensive?

the engine was a marvel of engineering. I got it to 400K+ miles (odometer eventually broke), and I could drive just fine even after my alternator broke and I had no electrical power whatsoever. I also could (and did) do extensive maintenance myself because there were no computers to fiddle with and everything was modular.

Any carb car, or even plans. Though you can argue an array of vacucum lines exist in 90's-current cars today because of emissions.

There's also the car community idea of a clean engine bay, or wiretuck.

https://preview.redd.it/3ddncz8e2ao21.jpg?auto=webp&s=e75f4a...

to

https://imgur.com/nuZGt

The federal government had super strict emission laws for vehicles starting in the 70s. This was before computers were cheap and reliable enough to stick in average vehicles, so the way automotive engineers got it to work was to have vacuum lines to send signals to the carburetor and distributor. They probably could've done it with analog electronics, but you already have a free source of vacuum (the intake manifold), and there isn't an simple way to convert an analog voltage to a linear position, while you can do that with a diaphragm and vacuum.

For a good example, any American V8.