Because those gate models can be hooked up to complete Portable Gates and fully synchronized! It gives the opportunity to train on a virtual 2-rider gate or even more if you want to connect up to a 4-rider gate. (Need to purchase separatly our gate hub and larger power supply)
We prefer having 2 individual gates than 1 solid 2-rider straight gate because of the budget, the portability and also the capacity to not have the gates perfectly aligned (the best when you have two riders with different levels : the best one will train on the gate behind to still improve and learn to pass)