This is nowhere near a product problem. The setting is per-account, so it's not like it'd be disabled on one device and enabled on another, so they'd get some weird UX, they just like crippling their app to force you to give them data.
I work for Google, opinions are my own. I could go on and on about this so apologies for the long post.
Obviously I am biased, but I think you're being a little too cynical.
People's habits largely depend on the incentives given to them. There is no incentive for the Maps team to take in more data, if anything there are incentives to have less data because they'd have to go through less security and privacy reviews.
What they DO have an incentive to do is to get more users, since that largely determines how much funding your team gets. Having users share location data, admittedly at the expense of privacy, provides a superior experience.
Each team has limited funding/headcount, so obviously they would use their resources as much as possible to try and get more users. Supporting the use case you described, which is not used by the vast majority of users does not align with the incentives given to them.
Recently, Google updated its values (I can't find it externally but I hope you'll believe me). One of these values is "Respect the User". I personally think that your use case would fall under this umbrella. Ignoring whether the specific feature is the best use of engineering time even for this value, the reality is that values mean nothing without incentives.
And there aren't incentives. You don't get a great performance rating for following the values, you get one for impacting some large percentage of users or improving the performance or conversion rates.
Even if you had a team of monks, completely driven by their morals and not career-driven whatsoever, this would not be sufficient because if they didn't hit performance goals then the team would just get defunded, unless the person above them was also the same, and the person above them, and so on.