What sort of industry are you in?

I work in consulting where people in my industry don't leave often for less than 20%, the rule you cite. The main reason is because in our industry, we expect to get promoted to next level every 2-3 years and in many cases, shifting to a new firm without a promotion can mean you delay that next level up by a year plus (most firms want you to be at level there for at least a year even if HR says otherwise).

As an example, 8 years ago, I got an offer for a 10% bump to leave to another firm when I was a year away from promotion at current firm. Turned it down and got the promotion which came with a 30% bump.

The bump across the board seems good if this isn't relevant to you.