It could be and there are a lot of accusations about why it isn't there but we really don't know for sure why Verizon isn't allowing it. Sprint has for a while on most phones, AT&T recently announced that all new phones will have FM working, I am not sure about TMobile. Verizon does not have it and does not have plans to have it as far as we know. I can only assume they have their reasons though I cannot imagine what that might be.
A recent theory I have read that makes a certain amount of sense is with FCC certifications. Though, I am not sure about that as what I recall from leaked FCC certifications the FM module is part of the cert. Also if you access the testing software built into Android you can test the FM chip. The chip works fine it is just blocked from third party apps like Next Radio and no first or second party apps have been provided.