What are the pros and cons of corporate tax breaks for recent graduates?

Hi everyone,
I am a recent economics graduate and have been thinking about youth unemployment recently, an issue that seems to transcend borders (US, UK, EU, China, South Africa, etc). I was thinking, what would happen if there were tax incentives to employ recent graduates for the first two years after graduation (any level of education)?

Not only would this help recent graduates get onto the career ladder, this should also result in increased long-term tax revenue as studies have shown that your first starting wage has compounding impacts on your lifetime earnings and savings. This one study found largely positive effects of a well-run tax incentive programme, without displacing those with just over two years of experience.

Here is this paper.

Besides a slight reduction in full-time schooling, are there any real downsides? Why do you think this isn't more widely adopted?