At this number of servers we can still host websites that have millions of users (but not tens of millions). They are not exotic servers either. In fact by now they are, on average, around 11 years old. And costed anywhere from 2k to 8k at the time of purchase. Some are as old as 19 years. Hell, when we bought some of them - with 32GB of memory each - AWS had no concept of "high memory" instances and you had to completely pay out your ass for a 32GB server, despite ram being fairly cheap at the time.
We have no dedicated hardware person. Between myself and the CTO, we average maybe a day per month thinking about or managing the hardware. If we need something special setup that we have no experience in, we have a person we know that we contract, and he walks us through how and why he set it up as he did. We've used him twice in the last 13 years.
The last time one of us had to visit the colocation center was months ago. The last time one of us had to go there in an emergency was years ago. It's a 5 minute drive from each of our homes.
So, why exactly should we use the cloud? We have servers we already paid for. We rent 3 cabinets - I don't recall the exact cost, but I think its around $1k per month. We spend practically no time managing them. In our time being hosted in a colo center - the past 19 years - we've had a total of 3 outages that were the fault of our colo center. They all lasted on the order of minutes.