You're at a restaurant with your kid, and they're bored because you're having adult conversations with your friends. You give them your phone and they play whatever game for a while, while you have no need for your phone because you're in a conversation.

Or, alternatively, you're sitting around the house and they want to play a game on it.

Call me old fashioned, but my parents just used to make us sit there and be quiet. Bored? That's life, learn to deal with it.

Both the parent and the child in your example are lacking discipline. The parent unable to tolerate a bored child and the child unable to tolerate boredom. This is a pattern I have personally noticed as early as babies being pushed around in prams with a smartphone or tablet in hand. A two year old definitely doesn't need a phone to relieve boredom but it's easy.

I'd prefer my children have something to do. A book, a phone, an iPad or Switch. Why shouldn't they be entertained while I am? Actually, forcing them to sit quietly while I have fun seems like a weird message to me.

Granted, being bored is a part of life. Undoubtedly then, they'll encounter many boring experiences without the need for me to artificially create them. And, if I know I'll have to wait for someone or something, I bring a book or phone. Why would I deny them the same pleasure?