The complexity and the fact that trading crypto to crypto is a taxable event in the US and possibly elsewhere. So if someone has to get paid in SBD to maximize the return from a post, but has to trade it for STEEM to get more SP and influence on the platform because they're a good little steemit citizen, then boom, they'd have to hold it for over a year to minimize the tax damage. It is a ridiculous system that creates huge tax burdens for no reason other than a convoluted desire to achieve what currencies by design in open markets cannot do and it certainly scares away many possible investors who are rightfully worried about the tax burden because of how the two coins are generated and need to be traded all the time.