The URL shortener is certainly a stretch when it comes to the primary goal of ad blocking. That totally makes sense and I consider that a “nice to have” and a neat feature.
The static DNS entries are a bit more fuzzy. To block ads most people are using the pi.hole as a replacement DNS server for their network. I’d put forth that since the pi.hole is used as a replacement DNS server, being a good DNS server is part of the core purpose of the project. Not the entire or primary purpose, but part of the method used to achieve that purpose.
Having the ability to set static DNS entries to hosts in an internal network would allow me to use the pi.hole as the source of truth for DNS on my network. That makes it a complete solution in regards to DNS entries and resolution and makes it a better all around solution. That means I don’t have to run separate infrastructure to supply those static and local entries. I hope that makes sense.