The costs ot implementation/risk/profit ratio isn't good.What crypto are they going to implement?BTC,ETH,ripple?Are they going to create samsungcoin?
Another thing is that Samsung Pay can't compete with other payment services, regardless of what they are doing, so crypto might help them gain more market share on that front as well.
In other words, it's a win win for Samsung since there isn't much to lose. It's either do nothing and lose market share, or be innovative and potentially make yourself relevant again. Easy option if you think about it....
And free marketing campaign as well for both. Not to mention the fact, that it could be a thing which most of the smartphones miss nowadays - real innovations. Of course, Samsung would not be the first one to implement the function, but as Apple does, make someone's innovation mainstream.