You are trying to compare the warm and the soft.
You will hardly find any vacancies only on WP, because only web-studios deal with WP. But they have a number of other CMSs in addition to WP: Bitrix, Joomla, OpenCart, Drupal, NetCat, etc. Therefore, if you get a job in a studio, you will have to work with all of these CMSs, and knowing only one WP will not save you.
WP is not needed for continuous support. You set it up once, you have it all set up, and it works. That's the end of the backend. Plus, there are practically no complex projects on WP. After all, it was originally positioned as an engine for blogs.
The frontend (and Vue) is another matter, where the interface and design can change very often. Because this is what the users of your application see. They don't see the backend, they don't even know you have WP. They see the frontend: all those animations, scrolls, sliders, beautiful forms. And that's the versatility of frontenders. They can do anything with Vue, they can do business card site, online store, bank, stock exchange, social network, and so on.
So the answer is simple - it's all about versatility.