Give me just one reason why deleting an old, long abandoned thread is better than simply locking it
If an old thread is full of spam and people using it for nothing other than to boost their account's post count/signature earnings, it is appropriate for a thread to be deleted in order to make it more difficult for those who used the thread for that purpose to fulfill it
So just locking the thread is a no-op?
If so, what about those non-spammy posts in it? These will get deleted too, as far as I can see? Did you ever wonder that it is a moderator's job to delete spam posts as fast as possible so that it never comes to deleting the whole thread (provided it wasn't a spam thread right from the start)? In the OP I meant specifically the threads that are no longer posted in, i.e. necrothreads (I thought it was evident from the context). The threads that are still active and old at that cannot be spammy by definition (as a whole, apart from individual posts), so they are just out of question altogether (it's no use trying to concoct impossible combinations here as it better suits your point), while deleting them would raise a lot of noise on their own. There were a few long threads about Gold vs Bitcoin, and they all had been locked, with only one remaining open. In short, I mean non-spammy abandoned threads created months if not years ago. Why should they ever get deleted and not locked (if necroraising is disallowed)?
Oh, I remember that at first, you claimed that I talk only about what could (theoretically) happen (meaning that it might not happen at all), and now, after the fact, you tell me that "they thought it would be more appropriate"
Were the posts deleted in these threads posted by more than one person/account? Were the posts deleted in these threads of any actual quality, meaning they added something to the discussion? Was the act of these posts being deleted a single isolated incident?
Wow, now it's no longer "they thought it would be more appropriate". I guess you are already past the point of back-pedaling this issue. But you may still ask hilarious (if you are really curious)