That is all true but then you need to pay for the services and equipment as well as have the expertise on staff to configure and manage the equipment.
As far as reliability, you can't compare almost any COLO location with an AWS data center.
As far as reliability, you can't compare almost any COLO location with an AWS data center.
There's no super secret reliability technology. You can absolutely compare colo with AWS. Many colos may be less reliable, and some may be more reliable. You need to look at power redundancy: how many utility feeds, what kind of ups, generators, testing schedules, what the points of failur are, how they responded in the past, etc. Same for networking feeds. Most colos have simpler networks than AWS which reduces the possible failures, but they may be less redundant etc; they probably have better bandwidth prices though.
Anyway, if you want a reliable system, you're going to need to be in multiple locations, and if you're in multiple locations, you should be able to weather the inevitable power relay failures and border router failures, etc every couple of years.
Why not? We had much less downtime than AWS' NoVa DC while coloing, and I don't think our DC was exceptional. AWS is probably much more competent, but they're also trying to build something much more complex than your average small-scale colo setup.