In many big companies, like Volkswagen, it is the choice of the team what tech stack they want to use.
In the past, many teams used Spring (Boot) because of the Java hype, but nowadays you either need maintain the server (you rarely change the webserver framework) or you start developing a new application, in that case they either keep using Spring Boot because they like/know it, or they use a completely different framework, like Ktor or Micronaut or a Go based server or nodeJS.
But often you also use the provided middleware that calls your application code.