I think its also a matter of funding and company financials as well. You have to make money to justify spending money and each company has a different idea on w

I think its also a matter of funding and company financials as well. You have to make money to justify spending money and each company has a different idea on what an acceptable infrastructure spend is. While it might be great to spend a ton of money and build a bullet proof infrastructure, if traffic slows down or revenue dips they are in the very negative position of having a lot of hardware and not a lot of money in the bank. They have to scale at the rate their revenue or financial backers will be able to sustain. Based on the number of new users signing up to the service the down time is not yet a significant deterrent. If use drops because of downtime they will likely need to reevaluate a large capital spend to solve the issue.