I think we see eye to eye here? I personally believe a lot of my engineer friends do not realize that they need to manage their career as much as they manage their technical skills. And that's why I suggested getting an outside opinion about one's market value annually (and if turns out to be a compelling valuation, take it).
You don't need to interview with a bunch of other teams to find out what your market value is, though. You can research average salaries for the job in a given region. The reason tech people interview without intention of taking the offer is to negotiate a raise with their present company (I agree that's not a good idea, and anyway, it's better to leave and get a new job if you want a raise).
Nice job generalizing, you wouldn't work in HR, would you?
IMO the answer to whether you leave or not is "it depends."
I've taken the counter once for a 25% raise as I was in the middle of a project and I cared about finishing it, but I usually leave if I find out I'm significantly (20% or more) underpaid (twice).
Glassdoor and meetups do not give personalized information about one's value. They only give average compensation data. The only way to get what you personally are worth is for you personally to get offers. Feel free to disagree.
