Agreed, the same two teams are always at the top of the standings. My reasons for why this is the case:1. Weak opposition. Let's face it, John/Scott, Lisa/Joni, Wanda/Desiree, and Danielle/Dani were all lousy racers.
2. Weak opposition, part II. Most of the remaining teams are mediocre racers. Ray/Yolanda, Lake/Michelle, and Monica/Joseph have shown flashes of competing with the top two teams, but all are mistake-prone and inconsistent. Fran/Barry and Dave/Lori are washed up and will be Philiminated soon.
3. Strong racing. BJ/Tyler and Eric/Jeremy are consistently good racers. BJ/Tyler are particularly good at taking advantage of opportunities, such as the Internet flight booking in the last episode.
Reasons for why things might change:
1. Bunching. The great TAR equalizer, each time the teams bunch up at an airport or due to "Hours of Operation", everything gets reset. Sooner or later, this will catch up to BJ/Tyler and Eric/Jeremy.
2. Mistakes. Eric/Jeremy in particular have made mistakes along the way, but have always recovered due to their youth and athleticism. That won't last forever.
3. Stress. As we started to see in the last episode, race stress plus jet lag and/or exhaustion started to make normally stable teams get snippy with each other. This will only get worse as the race goes on, and eventually it will affect everyone.