Do you have a link to the commits that removed the code. It'd be good to see what sort of complexity this sort of strong consistency can make redundant.
In the case of Hadoop's S3 connector, this could eliminate this entire directory, plus its tests, plus a bunch of hooks in the main code: https://github.com/apache/hadoop/tree/trunk/hadoop-tools/had.... There's an argument in favor of keeping it in case other S3-compatible stores need it (though you'd still need DynamoDB or some equivalent) and because it makes metadata lookups so much faster than S3 scans, which helps with query planning performance. But I imagine even fewer people will take the trade-off now that Amazon S3 itself is consistent.
disclosure: I work at Google as well.