Making them deflationary is more of a political statement than anything else I think. The crypto-currency crowd has this libertarian streak and of course those people believe that inflation is the devil, used by governments and banks to rob productive businessmen of their hard earned money.
Deflation also helps creditors and hurts those in debt, so it swings both ways.
Often the Libertarian/Austrian-econ crowd posits a false choice between deflation and hyperinflation, both are bad, and ignores the third option which is an inflation rate that's non-zero, but low and stable.
