I always copy my save as soon as I finish worldgen and get a world I find interesting, and don't consider it save-scumming to do a "total world reboot". "Savescumming" is trying to take advantage of the RNG by just reloading until you get a result you like. Restarting your whole world from the initial point is not the same thing to me at all.
It's also useful for Legends Mode.
Plus, NetHack is a game that's all about the challenge. I play DF more as a game about the science. I won't hesitate to "savescum" when it comes to just trying to understand things. In fact, back when I was first learning NetHack, I would "savescum" not to win, but to try new things out, like repeatedly stepping on polymorph traps to test out how many different things I could possibly turn into, and finding out I would do things like lay eggs in my own boots if I were polymorphed into a scorpion, then transform back into a humanoid and have baby scorpions following me around.
Savescumming is only a bad thing when you are actually taking the game seriously and as a challenge to survive or something... the game's not really all that hard, though, and you have to create your own challenges when you have any clue what you're doing. Savescumming is a bad thing when it sucks the tension out of the game because you can feel safe doing stupid things without worrying about the consequences, and having a real sense of danger and that you might lose something makes games like NetHack have tension. DF, though, I play controlling every possible angle. The only surprises I have are a few careless cave-ins I've caused over the years, and I am extremely conscious of managing all pathways and "safe areas" for my dwarves. I don't really get surprised that often anymore. I play for the architecture and the creativity, not for the tension.