[robryk]

I'm surprised that they aren't also available in some subdomain of dns.toys (so that they would resolve without using a special name server).

[quesera]

If you used default nameservers, you'd be introducing all the usual DNS complications, e.g. caching.

[avidiax]

Those complications would be easily controllable using the TTL.

[quesera]

Many ISP caches do not respect TTLs.