It is estimated that between 30% and 50% of Internet users run ad blockers. I haven't see a single ad in years.
Besides, Pi-holes are kind of overrated. First, ad blockers running in the browser are simply more effective. Second, Pi-hole is kind of heavy for what it does; you can accomplish the same by loading a blacklist directly to the config file of Unbound/Bind/Dnsmasq.
But for my use case, I like having the Pihole UI to see the charts and it's nice for temporarily unblocking one domain, etc.
Here is an excellent alternative to running Pihole that I've used before: https://www.geoghegan.ca/unbound-adblock.html