Why don't we always use the MobileNet?

Course Q&A Deep Learning Specialization Convolutional Neural Networks
1

After finishing Week 2 I was wondering why we build a mobileNet only for weak devices like mobile phones. Couldn’t we build way bigger network with it as the computational cost is so low?

2

Have you seen this page ? If you are willing to spend more on processing power / memory, building a bigger mobilenet might not be the best solution.