There are quite a few NCE stations that are simply non-profits per the laws of the state where they reside. They operate like any other NCE but their 'donations' and underwriting are not tax deductible although perhaps on state taxes if the state allows such. The other things is a non-IRS approved entity has virtually no chance at any grants except through some back door method. Since many businesses that buy underwriting write it off as a business expense under advertising/marketing, they would not want to take the deduction as a donation. Plenty of listeners that would contribute do so because of the station versus the ability to take a deduction on their taxes. The truth be told, many do anyway as the amount is minimal and they have little concern over if the entity they donated to was a 501c3 or otherwise.
Most such stations are smaller NCEs perhaps without the connections, knowledge and budget to go for a 501c3 or they prefer the concept of less scrutiny via a state non-profit status. As an applicant myself, the 501c3 can come later. It is too time consuming and for me, costly as I'd hire someone that knows what they're doing. The way I see it, is once I test the waters we'll either go for it or not but certainly not with dollars from our pocket but rather dollars already obtained by the non-profit. I know the IRS likes to review you via your website (you almost have to have one for 501c3) and they watch what you do to be sure you don't jump over the boundaries of what you can do. That stuff gets a little tricky sometimes. Still I recognize a 501c3 is likely the option all should aspire to.