You have to remember that the game is played by many different players in many different countries.
Bolton Wanderers, Blackburn Rovers, Leeds United etc. are quite big clubs in the UK, but because they don't play in the BPL any more they aren't known world wide. So you can't say they're not famous, each club has thousands of supporters, so thousands of potential customers for Nordeus
Dynamo Dresden has quite a large following.
The club store has Boca Juniors official merchandise, and i wouldn't call that team any where near as famous as some clubs that aren't mentioned.
Your comment was a little blunt and could come across as quite offensive to a supporter of Dynamo Dresden.
I think Nordeus are more inclined to stock items that a large amount of people would buy.
Eg, there is a large amount of people from Russia/Ukraine and Eastern Bloc countries playing, and i wouldn't be surprised if they end up stocking Anzhi, Zenit, Dynamo Kiev, Spartak merchandise etc, yet you wouldn't consider these teams as massive on a world wide scale.
It's all about demand at the end of the day.
EDIT: these clubs that you wouldn't describe as 'famous', would also have quite cheap licensing fees, i'd assume, so it's even more of an incentive for Nordeus to think about obtaining them.