Every single one of them was deploying the projects on the internal infrastructure, sometimes a small Kubernetes cluster, some other times just an EC2 instance, most of the time just one or two VMs.
Each employee was given a computer with a VPN client pre-installed, to connect to the internal infra.
The biggest company I've worked with had 10k employees, still not enough to see any impact on performance on the slowest single-threaded service we made.
When deploying, we were simply adding to the internal DNS server an A record "service.internal-domain.tld" pointing to the IP of our server. No load balancer, no reverse proxies, no HTTP/2 in the stack.
It's cheap, it works, it's certainly not something you would do if you were serving a SaaS application to millions of user on the world wide web, but it's definitely enough for internal stuff.
Even Google does not have more than 100k of employees.
However, turning on http2 for an org might mean nothing more than toggling some settings on a reverse proxy, no code changes required and little to no visibility or fuss for developers.
Alphabet has over 150k employees.
https://www.sec.gov/Archives/edgar/data/1652044/000165204422...
How do you know? Most of the Alexa top 100k web sites are HTTP/2 but I suspect a great many of the people working on those web sites have no idea HTTP/2 exists, it simply has no impact on their work. It probably has no impact on your work.