I know a few kids that had those when I was in Elementary school and I was never sure how they worked. But nowadays, kids are just handed the newest phones and honestly I don't know when I'd want to give my kid a phone nor what kind of phone I'd want to get them. I don't want to get something expensive in case they break or lose it, but I still want them to be able to use it with their friends. And with me being me, I'd definitely put some security stuff on it to make sure that my kids are only sending and receiving appropriate content with it.
Also, happy belated birthday and welcome to PC!
My dad's work is directly related to software and security and he can be over protective at times hahaha. But actually a few months ago he decided to trust me and decided to give me the PIN (you needed a PIN to add more phone numbers to this phone) to add my own numbers "until I saved enough to buy my own smartphone" (I actually didn't mind that silly phone as it did everything I needed (except for texting) and I'm saving for something else, but I was surprised when he gave me the phone on my birthday nonetheless ^-^). I still couldn't text my friends but I was able to add a few of them to call them.
I think smartphones have parental controls, but it makes me happy my dad decided to trust me and not enable them ^-^. I'm mostly interested in journal apps so I won't be betraying his trust.
And thank you very much for the welcome and congratulations ^-^!