Firstly, it's probably mostly representative of the country of origins demographics:
German 91.5%, Turkish 2.4%, other 6.1% (made up largely of Polish, Italian, Romanian, Syrian, and Greek)
Secondly, it is a common problem in most games:
http://adanai.com/gamer-demographics/
"Gamers have responded to the diversification of games, but oddly, games haven’t done as well at responding to the diversification of gamers. Many game companies still cater to very narrow demographics, with casts dominated by straight white men. Too often, female characters are relegated to nothing but eye candy at best, and minorities are very underrepresented."
Thirdly, a large part of the general problem is who is developing games:
http://www.newsweek.com/2016/10/21/video-games-race-black-protagonists-509328.html
"The International Game Developers Association suggests that only 3 percent of game developers are African-American, a figure that has risen by only 0.5 percent in the past decade. In comparison, 76 percent of developers are white"
Conclusion: There should be more diversity in all games but that probably won't happen until the root causes of who is developing them and more importantly who isn't and why are addressed.
I support lots of more avatars and ways to personalize them but yes there at least should be several more default beginner ones that represent more players.