To be hired as an artist or an architect, you need to present a portfolio which showcases years of your work. Programmers need a Github/StackOverflow account to showcase their contributions. Similarly, Kaggle is positioning itself in the same way for any data vocation. The litmus test to be hired as a data scientist gets another hoop. Kaggle has spent the last half decade positioning itself as the premier platform for hiring, recruiting, and screening for data science talent. Companies and recruiters get a transparent record of your performance, a paper trail of your successes and failures, and most importantly, your growth- all of which is tracked in a quantifiable manner. Employers want to see whether a candidate has been battle-tested in data science through these competitions.
To you as an individual, this is a chance to participate and compete against others like you from around the world, prove to employers and recruiters that you have some hands-on experiments under your belt, and that you are worthy of the title of Data Scientist.