Why ad servers don't just use direct IP addresses rather than DNS

[baronmax]

This is my stupid question:

If ad-servers are being blocked by pi-hole because of its DNS lookup entry why aren't the ad-servers addresses directly embedded as an IP address in a web-page rather than a DNS entry?

For example I can ping 162.125.19.9 which is the IP address for telemetry.dropbox.com but I can't ping telemetry.dropbox.com because pi-hole blocks it, which is good. But why don't the ad servers just embed the direct IP address?

Is it just because not that many people use pi-hole in relation to the whole internet, so not a major issue for ad server providers or is it because they are obliged to use DNS name addressing for efficient operation of the internet? (I know the reason for humans to use DNS name addressing because it's much more convenient to remember www.bbc.co.uk rather than 151.101.64.81 for example - but this doesn't apply to computers...)

Then follow on question: if some ad-servers do directly embed numeric IP addresses would it possible for pi-hole to block these as well? I think probably not because these would just go through the router but maybe I'm wrong...

Thanks!

[DanSchaper]

Because you can't load balance or update an IP address.

And no, Pi-hole can not block IP addresses, you'll need a firewall for that.

Edit:

nslookup telemetry.dropbox.com 8.8.8.8
Server:  dns.google
Address:  8.8.8.8

Non-authoritative answer:
Name:    telemetry.v.dropbox.com
Address:  162.125.35.136
Aliases:  telemetry.dropbox.com