Why is there only a 'streaming API' and nothing like 'realtime updates'?


Why is there only a ‘streaming API’ and nothing like ‘realtime updates’ with a callback URL, which would save both Server- and Client-Side progressing power? A lot of apps send push notifications or something similar to their users, but using the streaming APIs depends on having a thread for every single user, which is a high waste of progressing power and simply not affordable for companies or developers without own servers.