The other thing to realize is that, at least in the USA, they'll do everything they can to deny you medical benefits for injuries suffered in basic training, and this will persist after you get out, i.e. Veteran's Administration health care is pretty poor by all accounts. You can't just trust the system to look out for your interests in this area.
In addition, the 'educational assistance' is barely enough for a two-year vocational training program, certainly nowhere near enough for a full four-year college degree. It's better than nothing, certainly, but the advertising and the reality have a big disconnect.
If you're a teenage with zero alternative options and are completely desperate for a way out of an urban slum nightmare or a poverty-stricken rural life, the military is there as an option. I was once in a similar situation but I rejected military service because I'd heard too many Vietnam vets tell horror stories about how they'd been treated by the military. It wasn't much better for those who had to serve more recently in Afghanistan and Iraq, for equivalently dubious reasons.