We are forced to pay extremely large sums of money to upgrade our infrastructure as any purchase requires a redundant piece as well.
For example we have used 90% of our SANs storage, our IO is suffering and now were looking at purchasing two $10k SANs to upgrade. In the meantime, we have probably spent over 10k worth of development time to compress, clean up, and remove any data we don't need. We will not get the weeks of development effort back, we will continue to spend more money on hardware, and we will continue to suffer to delay projects because of poor choices.
If we had AWS, we could have written an entire sprints worth of work (also ~$14k worth of IT time) and moved on with our lives.
Clearly, some companies let the budget keep growing, but for most companies AWS flexibility is worth its weight in gold.