Even without a full hack, exposing IDs can allow competitors to "scrape" your site by simply changing the numbers in the URL to see every entry in your database.
It often indicates that the site may not be "sanitizing" its inputs, making it easy for bots to find and exploit. How to Protect Your Website
Students of ethical hacking use these specific parameters to practice identifying entry points for penetration testing in controlled environments. The Risks of Exposed URL Parameters