I remember, as a kid my mum always had an infinite amount of toys and things to keep me entertained in situations like this.
And for example eating out when I was a baby, my parents would always take it in turns to take me outside for a walk (whilst letting their meal get cold) so as not to bother other diners. They couldn't afford a babysitter, but they'd do their best in the situation.
Occasionally, people commented to them how good a job they were doing.

Because I grew up with it, I assumed it normal at first. Today, I sit in restaurants and listen to a screaming baby, while the parents just ignore it and continue eating, and it makes me realise how many people just don't have consideration for others, and think their precious child should be worshipped and have priority over everyone else.

On the occasion I do sit on a flight or in a restaurant where I barely hear a peep out of the child (and admittedly it's easy to overlook when they're quiet) or I can hear the parents trying really hard to keep them happy, I now always try to make a point of telling the parents what an amazing job they're doing and how much I appreciate it, as it really is refreshing when you do see it.

There are a small number of decent people in the world