As to an installer -- the JDK does not require any installation (just point JAVA_HOME at it). In addition, the JDK is for developers only. The days of the "system desktop JRE" are over, and it is against the recommended practice to have the JDK on non-developer machines. Instead, the recommended practice is to have the developer create a small custom runtime with jlink and bundle it with their application (or perhaps a runtime shared for all of the developer's applications, in case the users are all in the same company).
The JDK is for "developers only" because it is open and java is not. Oracle cannot tax and legally threaten an open system the same way it can one where you need a license to actually run java.
Just to be clear: Java is a standard; OpenJDK is the name of Oracle's implementation of the Java standard.
That the JDK is for developers who then build their own custom runtimes using the JDK tools is a result of shifts in software distribution -- on the desktop, the shift to app stores, and on the server, the shift to containers -- that made the "desktop JRE" irrelevant (and unpopular). But if you prefer that old model, the JDK contains all you need to create such a runtime easily.
Also, complicating things a bit if you want a traditional shared Java installation, AdoptOpenJDK has apparently been refused a license for the test suite, making it not quite properly offical Java.
Developers will continue using the JDK (for which no installation is necessary; just setting JAVA_HOME). A tool suite intended for users will share the same runtime. And when it comes to small, user-oriented, standalone utilities, Graal's native image makes that more compelling than ever.