「少数派OSとしての特徴」じゃなくて、伝統的にそうだったってだけ。
LAN 環境で使う分には、サービスが上がっててもさほど大きな問題じゃなかったからね。

まぁ、そういうユーザが増えたから次のリリースあたりで変更になるんじゃない？
Express ではすでにそうなってるからね。

http://docs.sun.com/app/docs/doc/819-2183/6n4g726ue?a=view
Network Services Startup

This security enhancement is new in the Solaris Express 7/06 release.

Starting with this release, the generic installation has been changed.
This change ensures that all network services, except ssh,
are either disabled or restricted to respond to local requests only.
The change to the generic installation also minimizes
potential vulnerabilities that might be targeted by remote attackers.

Additionally, the network services startup feature enables customers
to use only those services that they require. All of the affected services
are controlled by the Service Management Framework (SMF).
Any individual service can be enabled using the sycadm and syccfg commands.
The netservices command can be used to switch the service startup behavior.