This is one of the main reasons why I keep using Tor daily. The more people use Tor for normal browsing, the less interesting it becomes to be a Tor user, the better the anonymity for everyone else.

Quoting Phil Zimmermann:

What if everyone believed that law-abiding citizens should use postcards for their mail? If a nonconformist tried to assert his privacy by using an envelope for his mail, it would draw suspicion. Perhaps the authorities would open his mail to see what he's hiding. Fortunately, we don't live in that kind of world, because everyone protects most of their mail with envelopes. So no one draws suspicion by asserting their privacy with an envelope. There's safety in numbers. Analogously, it would be nice if everyone routinely used encryption for all their email, innocent or not, so that no one drew suspicion by asserting their email privacy with encryption. Think of it as a form of solidarity.

Would tor be better off if a major (millions of users) free software or browser vendor added always-on tor exit nodes to their releases?

The only solution to this problem that I can see is massive no opt-out adoption until a tipping point is reached.

I also use Tor sometimes for the sole purpose of muddying up the waters for investigators.

Similarly, I use it to train my internal neural net to better answer Cloudflare CAPTCHAs.

I use it to get around many paywalls.