I wouldn't quite say that this need is unacknowledged, most DBs have some kind of streaming interface for actual data contents (not queries, though), which for instance are leveraged by Debezium to expose change event streams in one uniform event format (disclaimer: I work on Debezium). Going foward, I expect that these capabilities will be substantially built out, also providing streaming query support (incrementally updated materialized views), not being locked in separate licensing layers or a more or less complex to use after-thought, but a primary part of database offerings, just as SELECT today.