If you're only applying for advertised roles it's likely that you're missing out on a variety of job opportunities, particularly... To gain access to this hidden jobs market a speculative application is usually necessary.
Speculative applications often provide a more direct route into a company and making contact with people of hiring authority can lead to:
temporary or permanent work;
internships or work shadowing opportunities;
increased business connections.
Read more at this UK website https://www.prospects.ac.uk/careers-advice/applying-for-jobs/how-to-write-a-speculative-job-application