The reason I discuss my salary details openly with friends and also share comp of others in the ecosystem (anonymized of course) is because for a long time I thought I was making a very good salary before I realised what the actual band for someone of my years of experience is.
There was no Blind earlier so what you knew depended on the network you had. And as you grow in your career, the band becomes bigger. So it is very hard to find a benchmark.
People generally don’t feel comfortable sharing salary info. Feel they will be judged.
But the worst is not even knowing that people are getting paid double your salary to do the same job, at the same level.
Not saying salary is the most important criteria for career decisions but it is helpful to know the band for your level.