Why is the maps app making any suggestions at all?

As much as Google apps annoy me (Android user), at least Google Maps still acts like a dump pipe. Silent unless called upon.

Because I drive there often at that time, and it saves me typing in the address manually.

That's different from what the OP was saying, which was seeing a Dunkin Donuts app recommendation, while he was in a different city, and didn't have a history of going to DD.

So your thing is not an ad, just an unnecessary reminder. I imagine after going the first couple of times, you don't need navigational assistance to get there.

How do you know that? Maybe OP often goes to their local DD.

OP: I've never used the Dunkin' Donuts app and had no interest.

So iOS is obviously not spying on its owner in ways that matter. If OP ordered from DD, Apple got that transaction and iOS started suggesting DD to OP across devices, that would be insidious enough to stop me from using Apple tech. Dumb location-based triggers are nothing, though I don't have them on because I need fewer distractions.

What feels as spying to me is, for example, seeing a specific medical care ad on YouTube after I talked to a friend about a health issue using a completely unrelated chat app or even IRL. There are clearly a lot of moving parts, a bunch of data stored outside of my device, and if it's not already tied to my identity it's likely de-anonymizable.

I at least personally appreciate it because when I get in my car after class (to drive the place I drive 90% of the time after class–home) it'll push an ETA onto my lock screen. It's not always right but it's generally very predictable (and can be disabled).