Using this method (and also, since recently, Theo's SimPE plugin "delete sim" in combination with Pescado's batbox, it's even faster and cleaner).

You must have patience then, I find it dull deleting one sim. I'm not patient I guess.

Well it has been done over several years, but you are right, it does please my simming OCD, I actually enjoy it (though I wish I could change font sizes in SimPE to spare my eyes). It's fast with Theo's tool, though, I used to make lists with three columns for name/instance/character, now I just need the name.
And it helps that I play on an old PC and therefore don't have (too) much CC: short loading times

The idea of deleting sims even the safe way makes me twitch. Why not just kill or ban them?

Because that doesn't remove them from the hood. I play the maxis hoods separately (not in an uberhood), that's six avatars of the same social groups, BV sims, downtownies, OFB townies, and so on.
To make things worse, at the beginning I added all three campuses because I didn't understand what they were and how they worked. Imagine the army of clone dormies everywhere.

Twitch like, because you find it morally wrong or because it could mess the neighbourhood?

The second! Sure as kids like candy I would mess it up. Before I made my new Sims 2 folder with no townies I just banned them with the visitor controller. Sure they are still there, but if I don't see them they don't bother me.

There's not much to mess up if one is careful to make a back up before, of course, and to use it how it was intended (not deleting wrong sims, family members...). That huge thread over at MATY is scary-looking but most of it is outdated or redundant info, even though you have to read it all to know that
I guess it's maybe.... safer? that it seems complicated, it is after all an advanced procedure that not everyone and every hood needs (like I said I had this invasion of dormies that is I think what made me start using it, IIRC), one of those "if you're not sure what you're doing and why, then just don't".

Surely it's easier and safer to make the neighborhoods in an empty environment? If you don't have the UC you can use AGS to make the hood and then copy the folder over; and if you have the UC or your computer doesn't like AGS for some other reason you can install empty templates.