BTC is a team that is focused on winning championships. They have a very specific training plan that is designed to help them achieve their goals. This training plan may not include racing as frequently as other teams, as they may believe that it is more important to focus on quality over quantity.
BTC is a US-based team. This means that they have to travel to Europe to race in most of the Diamond League events. This can be a costly dip into their sponsorship, grant and donation money and is also a very time-consuming endeavor. It simply may not be worth it for BTC to race in every competition you hope they would, not even around the US, and I'll share why.
What works for one athlete may not work for another. BTC is a team that has found what works for them, and they are not going to change their approach just because some random people on a message board are criticizing them.
Absolutely, Fisher and Cranny racing in Europe last year after Worlds was a welcome change, and I also think it's something that BTC should continue to do. However, it is important to remember that BTC is a team that is focused on winning championships. They will not sacrifice their goals in order to race more frequently.