I definitely preferred browsers bundling it, because it was one less security dependency I had to worry about managing. And considering Flash plugins were part of the "older model" of browser add-ons, bringing it in-house allowed browsers to better sandbox and secure it, and prevent other applications from exploiting the same way in.

And every browser bundling it also provided a setting (and corresponding enterprise policy configuration) to disable it.

I don't actually remember it ever being bundled up until Google Chrome?