In my opinion, the primary reason why we're not seeing a massive acceptance of NMC as decentralized DNS is the lack of usability.
Imagine all browsers supported NMC out of the box (e.g. including a light client which does DNS lookups) and you could register a name without hassle using a light client or even a web app. I think in this case it would be a serious competitor to centralized registrars - as a much cheaper way to provide the same service, and without having to deal with centralized services.
But we have not even a light client which can register names. That everyone should run a full node is a nice vision, but unfortunately, it's not realistic at this point.
And this is a chance for NMC investors - above all those that know a bit about coding, as they could simply port light clients, provide electrum server services, code browser extensions etc. It's also a risk, because another coin project can provide the same features - and maybe faster.
But I'm currently seeing some progress on these issues, and thus I've bought some NMC.
I myself is also a HODLer of NMC which I bought about a year ago when I first stepped into cryptocurrency learning that NMC is second coin after bitcoin and it has crashed more than 75% from ATH. I bought it without any knowledge about project back then. Now, about a year later I found that coin still in same place and after my some research, it is because lack of mass acceptance as well as people are not interested in these type of projects right now. It seems they have also failed to deliver. I may be wrong and the team is working hard behind to deliver something big in the right time once demand for decentralized DNS arises, but right now, its a speculation that something good is coming. If team able to deliver in right time, it will certainly be a big multiplier of the investment. I will continue to HODL this because this is my one of the initial coins I bought after bitcoin.