There’s also a lot of selection bias: that region is the most popular and people remember hearing about problems a lot more than the people who were unaffected but didn’t say anything about it.
I’ve had plenty of instances in us-east-1 for over a decade without downtime other than the 17 minutes in 2011 where they had a network routing issue which kept the entire region running but off of the internet. I never had that with a colo - power outages & backhoes - but several came close.
For me, I’d tend to focus the question on how screwed you are if something goes down. You can save a ton of money for a bandwidth-heavy service if you use a colo so it’d really be a question of how easy it is to make it redundant (short outage) and rebuild (long outage or permanent equipment failure).