Who's Hiring: No salary wastes everyone's time
Missed opportunity: company and candidate may never meet because candidate assumes low salary.
Wasted company and candidate time: candidate is enthusiastic and goes through some effort/process before discovering the salary is too low.
The days of hiding salary numbers need to end. Imagine shopping at some stores where the cost of items were not displayed until checkout. Shoppers would favor the stores which listed prices up front; they would only visit the hidden-price stores for unique or specialty items which were not available at stores which listed prices.
If a company cannot compete on salary, and they know it, they should explain why they are still worth considering. And if they have no value to offer to make up for the comparatively low salary, then they should make clear that they accept more junior developers (or are willing to train).