Because the second you post a wide salary range, people assume they are going to land on the mid-upper end of it no matter what the range is. If somebody lands on the lower end of it, they are going to feel slighted or insulted for just about all cases aside from new grads.
If I post a salary range of $50,000-$150,000 most people are going to look at it and decide that it probably pays $100,000-120,000. If somebody applies for that job and you offer them $60,000-70,000 they are going to be insulted just by the offer because of how much was left on the table (even if it's a perfectly good salary for the job).
Nobody wants to hear they are on the lower end of anything. That's why most people view themselves as "middle class".
If you post something that wide we're either looking at a sales position or at a company that does not differentiate between a Jr. and a Sr. Developer and lumps them all into Developer.
In itself it might be enough of a red flag not to work there.
Why can't a project just need developers? Maybe you need 2 or 3 across many skill ranges.
I think the best option is different posts with different salary ranges... but I do see how that can be a pain to copy paste data around (say 3 postings x 10 job sites = 30 copy pastes of the same data with a few different skills and a few different numbers)
If I post a salary range of $50,000-$150,000 most people are going to look at it and decide that it probably pays $100,000-120,000. If somebody applies for that job and you offer them $60,000-70,000 they are going to be insulted just by the offer because of how much was left on the table (even if it's a perfectly good salary for the job).
Nobody wants to hear they are on the lower end of anything. That's why most people view themselves as "middle class".