Maybe it was instilled in me by my parents so I might as well give them the credit. It's about "Doing what you say you're going to do".
It sounds simple. It sounds obvious. In my people-circle, it's a concept not taken seriously.
To be there at 3, I have probably made some modifications to my day. Like, maybe re-arranging a meeting, or making a special trip to pick up something. Maybe the person I'm having lunch with was late, making our entire lunch date run overtime, so I have to watch my time to keep my schedule so I'm not late for you.
But this "do what you say you're going to do" isn't just about being on time to an appointment. It's about everything. Say, I'm buying a item for dinner you asked for but I forget - now you're without your dinner.
So the spin-off effect of NOT "doing what you say you're going to do", messes up someone else's plans.
It's also a Biblical concept "Let your yes be yes" - Matthew 5:37.
For me, NOT doing what you said you would do, is disrespectful of me because not only do you leave me stuck, but you make me feeling like I'm unimportant to you.
Is it really that hard to do what you say you're going to do?