Because it only shows top 200 players.
You're #3201
This is true. "Sort by Streak" is our own little hack, where we show the top streaks but only out of the top 200 players by ELO. We asked for a genuine "Top Streak" hook from Relic so that we could get a sort of the entire database, but we haven't heard back.
So really to be more precise, our "Sort by Streak" is actually "Sort the Top 200 ELO players by Streak." Hope that clears things up. It's the best we can do at the moment.