Why don't people value their word anymore?

The problem in the world today is you can't depend on anyone for anything. You should always strive to keep your word. If you say you're going to have something finished tomorrow, make sure you have it done tomorrow. If not, be honest and say it can't be done up front and you'll need more time. Seriously, why is it so commonplace and accepted to have to keep following up with someone and stay on them to get them to do what you need done?