Your point is that training is computationally intensive, but your question is "why do people obsess over training"? Sounds like you've answered your own questi

Your point is that training is computationally intensive, but your question is "why do people obsess over training"? Sounds like you've answered your own question, then. It's currently hard to train networks, so people "obsess" over improving the methods (see, for example, the article we're commenting on) so that it doesn't have to take as long. But also note that what you say is not necessarily true that the NN's spend most of their time training. Maybe you've got to spend a week on a huge GPU cluster training some autonomous-driving algorithm, but then it runs in "compute" mode for hours a day in tens of thousands of cars.