Certain algorithms/models are implemented in PyTorch or Caffe and typically it's huge amount of work to convert them to TensorFlow while ensuring correctness / Parity. Also I personally like design of PyTorch.
coming from the facebook/reactjs weaponized patent grant problem.. caffe also has the same revocable patent grant.
Tensorflow is apache licensed. I think in general, the perception is that it is far safer to stay away from caffe.
Caffe 1 is developed by Berkeley and I think Apache or BSD licensed. The Patents.txt issue occurs with Caffe 2 which is developed by Facebook.