The problem is that it isn't enough to just know they are okay. As evidenced here - for years, his parents said they just wanted to know he was okay. They appealed for contact, saying if he just made contact and reassured someone he was fine, that'd be enough. No questions asked. But now they've been told that he is fine, and he doesn't want contact, they've hired a private detective. Their interview is all about how many questions they have, what they need answers too.
I didn't have children and I'm not married. I left my parents, and my siblings, and my foster siblings. For the latter group, I wanted to leave a note. I felt terrible for the younger children. The police advised me not too. Social services did the same. If I was going to go, I should just go - leaving a note just starts a trail. People will convince themselves that it's fake, or it was written under duress, or its' evidence of a mental health issue. The Salvation Army told me to try to pass on an anonymous message through their schools once I'd been gone for over a year and was somewhere safe, if I needed to do anything at all.
For him, as the news reports reference Social Aid in Spain being heavily involved and him having several alias' as well as his real identity, it could be that it's a health issue.
For me, it was necessary. I don't think I'd be alive otherwise. Me leaving also meant that Social Services took my sisters' care more seriously, and took them into care, which is what I'd been asking for for years. Until I left, they didn't care. It was still incredibly hard to walk away from everything - my school, my friends, extended family, my sisters - and know that for the vast majority of those people, they wouldn't see me again. We cannot have contact because you can't have roads that lead back to you. And 9 years later, I still live in absolute fear of them finding me. Unknown calls or unexpected doorbells give me panic attacks. When I do something good at work and they want to publicise it online, I have to beg them not too. I didn't just selfishly wonder off because I felt like starting a new life. Some people might, but for the effort involved, it'd be very few, I think.
As for wasting police time - I told the police of my plans and reassured them I was safe after I'd left. It would take an extra level of effort not to be traceable by the police either - no bank accounts, no mobile phone, etc. Not even just different ones to the ones the people you're running from know.