Restricted and or community gTLDs have varied and unique registrant eligibility restrictions. Therefore simply because a registrar implements one of these restricted new gTLDs, they cannot assume that they can replicate the implementation for all others. This in effect creates a barrier to entry for registrars that might otherwise opt to see the name, if only they did not have the added cost and complexity of the new gTLDs unique requirements.
Conversely, although the eligibility restrictions were designed to either secure the new gTLD or to create value within the new gTLD, these same restrictions now create a distribution problem by narrowing the potential number of registrars who would be willing to carry it. And currently there are no solutions available for either the registrars or the registry to simplify the problem.