5000 kids asking you for a job per month is a nuisance.
it's a great marketing platform, if anything. Strong brand loyalty going forward and costs you not much to do well, not to mention you can brighten a day or few for thousands of kids in all sorts of life situations.
You're severely mistaken if you think that's how businesses operate. Companies penny pinch on staff even for recruiting, they're not gonna increase headcount just to answer mail form kids just because you think it makes good marketing.
You can spin up any idea and claim it increases brand loyalty, but you have to have actual evidence that that either happens or actually matters in some way, and in this case it probably doesn't and isn't worth the expense once the scale exceeds >1 employee spending more than a few minutes a day. If you've got the data to prove otherwise so that you can actually make someone money, go ahead and sell people on the idea.
Because you actually believe the world is full of benevolent companies who work for the public good?
Or maybe people have seen what companies are doing behind the scenes that goes against their PR, making it worthless and hypocritic. Remember "don't be evil"?