The hassle is mostly prepping for the interviews. If I can't cut out that step, I am basically being saved the effort of cleaning up my desk and going to a new one.
I've gotten 10-15% raises before without a competing offer or any other leverage simply because I could show that I was a certain "percentage of market rate" when I was hired, but the market rate had increased ~teen% since then. So it wasn't as much me asking for raise, it was me asking to have my compensation keep pace with the market/inflation.
Also ask them if their company is hiring and has reasonable interviewing practices. Not everyone makes candidates jump through hoops.
1. People who are legitimately being taken advantage of can more quickly realize it and either work to correct it or leave.
2. Top earners should be able to justify their outsized compensation to others, including peers.
3. Some people just legitimately don't know you can negotiate things like non-discretionary bonuses, extra PTO, etc.
4. Maybe your company pays everyone below-market, not just you, and at least knowing this will make it easier to decide if it's worth the lower pay (for QOL/WLB or whatever) or if you want to leave.
Now, it's tough to say whether that can be extrapolated out to knowledge workers, but it is a useful datapoint non-the-less.
First step: ask for a raise, even a substantial one. You mightn't get it, but you might, and it's a lot less hassle than changing jobs