I'm not 100% sure about this but I think part of the reason why its called you only look once is that it is single frame object detection. I do know that there are other types of networks that can previous frames into account, but the models themselves are much larger (in terms of VRAM requirements for loading into memory) and more computationally intensive. This network is special because it can run with very little power. From what I remember it can run on a 10W board at 6fps which compared to networks only a few years ago is 10x decrease