You get in contact with new technologies which helps staying up-to-date as a pentester. Besides the normal boxes, I personally especially prefer the Prolabs.

When I started my infosec career, I began with HackTheBox. At first, you start with Easy machines, and you bang your head against the wall, wondering how to pop a shell or how to become an Administrator. But with every box you do, you can see your progress. Easy boxes become more accessible, and you start doing your first Medium or even Hard boxes. You start looking for a team and eventually find like-minded peers on their Discord server. And at one point, you even find yourself doing Insane boxes, banging your head against the wall until it finally clicks. And suddenly, you've got what is needed to be a professional Pentester. Long story short, everyone wanting to step foot into Penetration Testing will most likely start with HackTheBox. A sheer unlimited amount of knowledge waits for you to digest. And when you're done with all the "easy" content, there's always the possibility to do real-world scenarios in the form of Prolabs. As a Security Professional, you shouldn't miss out on this opportunity.

high quality, varied content, interesting challenges, and valuable community support and experience top creators (0xdf, ippsec, &c) content have been fantastic Competitors only have first mover advantage any more