Presumably this is their attempt at being "nice" to the various users of IDFA, who often times key off the IDFA to store a value of a user profile, conversion e

Presumably this is their attempt at being "nice" to the various users of IDFA, who often times key off the IDFA to store a value of a user profile, conversion event or other data. By using a fixed zero value, it allows said parties (be they ad networks, analytics providers, etc) to simply discard the record, rather than blowing up their DB with an unbounded number of useless rows.