They want to make sending of crypto no possible after buying with cash. I think they have noticed that most people that are sending cryptocurrencies to the scammers are lured by the scammers to convert dollar to crypto before sending.
I don't know if the if they may have some undisclosed intentions on that notation as it is also undoubtedly that the government too is forcing in to have its own sector paired with the crypto block chain to maintain relevancy of the dollar or in overall cash.
It is also true that bitcoin is not competing with the traditional currency but due to its fast growing and admirations of user's in facilitating transactions, the authorities fears that if the dollar is not effective in the process, the dollar might be fading out of its dominance.
So, suspending crypto currencies as means of processing transactions to other parties will keep the dollar relevance while emphasizing such authoritative power can only be effective in the regulating sectors such as the ATM spots.
In the other hand, the ideal is to keep track of user's and makes it easier to trap scammers.