Example: if you give administrators the option of putting a router
address in a DHCP option, they will do so and some fraction of the
time, this will be the wrong address and things don't work.

They cause themselves a problem then they fix it.

If you let routers announce their presence, then it's virtually
impossible that something goes wrong


because routers know who they are

It doesn't mean they're right.

If I choose DHCP I've made the choice to define how this network
works. I then want it to carry on like that, not depend on others
not screwing up too.

A clear win. Of course it does mean that people <gasp> have to
learn something new when adopting IPv6.

It means all administrators now have to guard against trivial
errors by all end users. Lot larger fail surface

It's not about dislike of new, it's dislike of pointless risk