One of the aspects I value most, is trust. I someone agrees or promises something, the moment they break that promise, my respect for them drastically declines.
Of course, something might come up, but have the decency to give a heads up.
Example A, you agree to meet at 10 am. The person you're meeting messages you at 10:10, that they're going to be late because they ran into an issue at 9:30. That message could have been sent 40 minutes earlier. At the very least, it could have even been sent 15 minutes ago.
Example B, someone agrees to do a task. A day later, you check up on the progress. They state they were busy and will complete it as soon as they get home. Another day passes and nothing has happened.
Both cases showcase perfect examples of absolute disrespect.