Reasons why I want user-controlled spawner blocks, even if it’s just in creative mode:

1) Squids de-spawn when you’re not looking at them
2) I want a room full of squids
3) Even if I add a cubic metric butt-ton of them before the last save, I’m scared they’ll go away before my adventurers get there
4) There are other creatures I want in my chambers that de-spawn at the slightest provocation.