but why go the roundabout way of surveying?

I would not call this "roundabout". Is it weird? Yes. But I actually would actually argue it's less roundabout than alternatives. What alternative would you propose?

I suspect most people would say "well why not put out a survey to users and ask...." but that comes with multiple known faults. 1) People's answers are not always genuine, and they can't always accurately forsee how they would react, which is a common problem in data gathering. And 2) How do you collect and sample those users? Sure, you have your existing player base, but what happens if your game is in a different genre and your player base wouldn't be the same?

I suspect that the second point is the bigger reason things shifted this way - ads are common in mobile games and mobile games are trying to sell to people already playing mobile games. Your audience is already reachable through ads, so why build a new system when one is already in place, being built by someone else so you don't have to do any work but make the ad?

But to circle back... When you ship your game, you're going to advertise it, and you want people to click on those ads, because that is how you get users. By putting out ads before you've built the game, you're literally sampling by using the exact system you will be using when you ship. And you're going to get data on whether users actually perform the behavior you want - to click the ad.

I fucking hate this, but to be honest... It's actually a perfect parallel... They're measuring exactly the end goal (efficacy of the ads) before they've built the product. It's actually pretty genius and lucky it works out. It's fucking evil, don't get me wrong, but it is actually a perfect gauge.

Any alternative, imo, is actually more roundabout.

isn't it counterproductive to lose users this way?

What users would they be losing? People already playing their game aren't going to see ads, click them, see they have it installed, then quit. So they're not losing existing users. They can't be "losing" users for a game that doesn't exist yet.

You could argue that the negative reviews on your original game will hurt it, but this process is usually done when they have a steady existing game. And those don't last forever. Once they've peaked, they've "served their purpose" in the companies eyes. And these negative reviews are way less impactful on successful games that have thousands of reviews already. And, the game probably isn't growing so they don't care. And they're relatively rare and the "hate" is far less impactful than knowing whether your next game is worth investing in.

You could also argue "well they're upsetting potential players they would have when the game releases" but they run these at "relatively small" fractions of their intended target audience, and the mobile player pool is gargantuan. On top of that, by the time the game comes out, people likely won't remember the ad, and they very likely won't remember it was a bait. And they may even change the art style or theme for release, and just leverage the same mechanics etc.