The government.
I wouldn't blame the government for this. Businesses are perfectly capable of accepting crypto if they so desired and payment processors like bitpay do exist. What I would argue is that merchants are just not interested in doing it, or at least not most of them.
There have been some governments who have banned crypto if i'm not mistaken, but it currently is not a systemic problem. In the US, there is a local restaurant that I know of that accepts bitcoin and the government has no problem with this. The truth is that its a pain in the ass for the business. They're used to cash and credit cards and those methods are fast and easy.
Also if bitcoin hasn't gained a foothold, do you really think altcoins are going to? I would argue that a good percentage of the world population doesn't even know ETH exists and they certainly don't know that coins like WAVES or LTC exist. Though I don't want it to be this way, the fact is that people are comfortable with banks and cash and plastic money. Those things are ubiquitous and crypto is not.
No government has forbidden consumers or merchants from using or accepting crypto payments. So, they aren't a obstacle per se.
Now, gaining governments enthusiastic support because there is a cryptocurrency designed to make applying their regulations easier and more efficient would be quite helpful. I see this being the opportunity.
People don't care about what cryptocurrency is behind a crypto payment. What they care is that there is some advantage to them for using crypto payments, that it is easy to use, and that enough consumers and merchants use and accept it.
That means there must be innovation on the mobile payment applications and POS systems to make these things happen.