Re: VPS
"I doubt anyone reading this will need to scale-out their web application to multiple servers due to the number of users."
Are you serious?
Have you ever worked in a large business, say one in the FTSE100? One with tens, hundreds or even millions of customers/users?
They probably haven't, and neither will most people. Because most businesses are not FTSE100s, and most people work for companies with fewer than 20 employees.
So there are two points here:
1. Who cares about tens of thousands of users? FTSE100s, sure. But not most people.
2. Modern silicon/servers are wildly, hilariously powerful and storage dense per U, when considering basic line-of-business applications like web hosting, mailboxes and file storage. You can host >20k mailboxes on a 1U server. Even for moderately Medium sized enterprises, you're looking at a couple of mail servers (for redundancy), couple of webservers, couple of fileservers. The whole thing is less than a quarter rack. But then you want another half rack in another location for failover. These are probably going to be Proxmox clusters running VMs rather than bare metal, but even with the inefficiency of bare metal (in so much as some U will always be significantly underutilised), it's not a lot of boxes, nor a particularly deep architecture. Bakc in the day, I started out at a company that had everything on a single server. They got a bigger one, then a bigger one. I thought "this'll be the last general purpose box we get. We'll have to branch out to DB/web/media servers next time". But Moore's law and storage density kept up. They split out stuff for redundancy and architectural purposes eventually, but the whole lot could still have run on a single box in terms of CPU/RAM/storage capacity.
I've been through a company that had a single server hosting their entire production environment, with a second (in a different DC) for failover, on a hot-cold basis. Their (third party) CDN ran health checks and transparently failed across if Prod went away. That was it. Then there were a couple of VMWare boxes for build nodes and some other small stuff that didn't justify bare metal. You'll say "can't have been very significant", and you'd be right - they were (are) a small firm <20 people with like, 10 customers that you won't have heard of - a mid-west concern in Illinois called John Deere, some insecty outfit called Caterpillar. A niche Korean bunch called Komatsu.
All live traffic was being served (at the time) off one 16-core Windows box, running IIS, SQL Server and a couple of other bits. Kind of terrifying, but also a testament that you can do a whole lot of very real, actually useful processing with modest resources.
In all seriousness, most businesses could host their entire infrastructure on a single 1U cPanel server - web, mail, etc and have empty drive slots and capacity to spare. Yes, you would like some redundancy, but in terms of the actual resource required to run the applications? That's it.
We get carried away in IT with racks of gear and five-9s. Especially when it's not our money. For a small business, their email falling over for an hour or for a reboot is of no concern. Certainly less important than making sure they have immutable, ransomware-proof backups. They receive less than 50MB of mail in 24hours and delete most of it immediately. That's the reality of the real world - in so much as most of the real world is shops and car garages and hairdressers getting on with their business, not software houses with a big old CI/CD build infrastructure, multi-cloud load balancing or any of that stuff.
