It has nothing to do with the individual FSDOs, but rather the individual inspectors. In the not-so-distant past there have been inspectors that were held individually liable for mishaps that occurred after a field approved installation in which the approved data was found to be a contributing factor. This spawned a jump in professional liability insurance policy purchases by airworthiness inspectors who feared being sued individually for simply doing their job. And what followed was a trend of inspectors just refusing to perform field approvals altogether. Compounding the issue is that the inspector force has shrank to a fraction of what it was only ten years ago and the specialized knowledge required for many field approvals just isn’t there anymore in the FSDOs. Or if it is, an applicant has to wait until that inspector is available. Which is why an applicant that has the financial resources is better off obtaining a designee.