That article smells a bit inadvertently jingoistic or ignorant. Belarus and Ukraine being listed as too small of markets is shockingly ignorant of the current state of the games. They are some of the largest and highest volume markets at the moment.
What Party meant by 'commercial reasons' is that these countries have too many winning players, as seems to be the windmills for the current sites Quixotian fixation in the search for a magic pill that doesn't involve changing the fact that they're raking the games to death. The sample given from this (
http://www.pokertableratings.com/top-countries-year) link at PokerTableRatings, while limited, is almost certainly also indicative of the market as a whole. Ukraine and Belarus are the 6th and 9th largest markets respectively. What makes them unique is that they are some of the only online markets that are winning money in the long run.
In fact if you look at the list of countries banned here it's basically a who's who list of winning to small losing countries. This has nothing to do with legal obligations.