In decks that might not have as much to do early as they build towards their more expensive cards, this serves as a great way to keep filtering through your deck and building up your resources to get there
The trade-off for that restriction comes in strength, of course
For some formats, there are even communities (such as Discord groups) dedicated to specific deck archetypes
By building a Sacrifice-focussed deck around Teysa, you can activate these death triggers at will
If you just love D&D and want an excuse to get into MTG, this set's Collector's packs are perfect to kick-start any collection
If Aang's Iceberg leaves the battlefield before the activated ability resolves, you will be unable to sacrifice Aang's Iceberg and will not scry, even if Aang's Iceberg was sacrificed via a different ability while its activated ability was on the stack