Speculating on currency prices is a business; it is *not however the business that digital currency infrastructure companies are in.
Yes it is. It may not be how they market themselves. But it's the principal risk they take and, directly and indirectly, the principal determinant of their profitability.
We take the risk as a service to the community, and the product is a cost center.
JPMorgan Chase could just as well say it issues mortgages and accepts deposits as a service to the country, that its retail operation is a cost centre for the real business of this or that. (It was popular, before the crisis, for banks to claim mortgages were simply a cost centre for winning wealth management and investment banking business.)
The business you're in is the business from which you earn profits and in respect of which you hold risks. Railroads and trucks [1], McDonald's and real estate [2]...this is an adage in business as old as commerce.
[1] http://www.lessonsoffailure.com/tag/railroads/
[2] https://qz.com/965779/mcdonalds-isnt-really-a-fast-food-chai...
One can loosely think of an appreciating cryptocurrency as a short-term loan. You're out cash up front. Later, and only later, you get it back plus a little more.
The infrastructure company in your example is thus, by turning cryptocurrency's promise of cash tomorrow into cash today, providing maturity transformation [1]. This is one of the core services of a bank. It is also an inherently risky business on account of the asset-liability mismatch.
[1] https://en.wikipedia.org/wiki/Maturity_transformation