You need to automatically report some search result on a schedule. For instance, you have stakeholders that expect to get an email every Monday at 10:00 containing the top most important security events for the previous week.

You have an ingest delay on some logs, which results in them never appearing in searches made by alerts. For instance, if an alert looks back in time using a 1h time window, it won't trigger on logs ingested with a 12-hour delay. With a scheduled search, you can choose to run your search at a point in time, where you're fairly certain that every log of interest has been ingested.

You need to take delayed action on search results. For instance, if you trigger user bans using an alert, offending users will be banned immediately upon a transgression and can then easily figure out what triggered their ban. Using a scheduled search, you can choose to ban all offending users at the same time every day, as to obscure the conditions of a ban.