For now. When their growth, or margins start shrinking, Wall Street will push hard on them to collect and monetize this data.
Remember when you paid a premium for cable TV, because it didn't have advertisements? Now, you still pay a premium, but it's 33% ads.
Building weapons wasn't in Google's DNA either, yet Maven happened. It was only shut down because the pushback succeeded. Its success was not a sure thing.
Corporations aren't people - the only principles or ethical compasses they follow are those of their employees. Employees come and go, and, in the case of leadership, can be fired by the owners.
There's a long history of tech companies that have done a 180, in terms of their DNA. Microsoft, SUN (Having been bought by Oracle), Google, are some of the more prominent ones.
No, cable originated as means to deliver broadcast channels, which had ads. You never paid for basic cable because it did have ads, because it always did. You paid a premium because you got a clear signal not degraded by distance and atmospheric conditions. And later because it offered channels (still ad supported) that you couldn't get over the air at all.
Now, even later, it was possible to pay a premium on top of basic cable to get additional channels without ads, but those premium channels still don't have ads.