A normal part of an interview process is discussing salary, and if they won't give an answer then you know they are not trying to be competitive and it's not worth continuing the process.
This is making the market more efficient.
Edit: Also, when a company does not disclose the salary range for the position it actually provides a very useful data point., You can pretty much be sure it's at most average -- but probably less-than-competetive -- market rates. The major and popular tech companies don't need to do this because they have a reputation, but the smaller companies can either show they too are competitive (by publishing above-market rates) or show they do not offer competitive salary (by not publishing their salary target).