I have seen no engine, company, software, game, or anything that needs to update their algorithm so frequently.
Well then you're grossly unaware of a product development cycle. Products receive several frequent updates.
Everything from how search appears in Amazon to product placement, even their Product Advertising API, to what movies are recommended to you in Netflix gets updated optimized. Your apple device gets optimized. The apps running them get optimized/updated.
For instance, here is Slack's update history -
https://slack.com/intl/en-in/help/articles/115004846068-Slack-updates-and-changes
For Google, search is and will continue to be their flagship product and they go through a development lifecycle continuously. This has been true since the early 2004.
Only difference is with the advent of newer toolsl, you're able to track it better.
For them semantic relevance is what matters - and that is the only thing they really care about. Think of the millions of websites and the several billions of web pages they crawl. They have to sift through this data trove to show the most relevant event.
For them, the only way to ensure their system is not gamed, is to remove all rhyme and reason to be able to rank.
Only that they do this in parts and don't push a major overhaul. They also rigidly test every update by pushing major/micro updates every so often.
As webmasters, you have only one job. Stay ahead. Keep developing. Keep pushing the envelope.