For me these are least important and I struggle to understand why others are so obsessed with it (this does not mean that I think current implementation is the best possible, I just don't care).
The reasons: if I see a badge on a program (mail, phone or SMS) I will check it anyway, so I don't need the full info on the home screen.
For me, it's convenience. My phone is laying on the desk, I can just stretch my hand, press the home button and instantly see the overview of situation. Easily distinguishable lines (courtesy of jailbreak and LockInfo) for missed calls, SMSes, emails, calendar events. What's more, unlike the default notifications, I get a little bit more information, allowing me to see that all the mails are from Facebook and can be ignored at the moment.
I don't cary my phone with me everywhere, especially when at home, so checking up on the situation is a common task for me.
I have to ask: have you ever used a lockscreen notification app? Once you do, you'll realize the value of having all the information that you might want to see at a glance immediately on your lockscreen.
LockInfo, for instance, lets you choose the type of information to display as well as how to display it. You don't see anything you don't want to see.
Then once you use something like it, you can't go back. There are a ton of people who jailbreak just to install LockInfo. That's how good it is.
The reasons: if I see a badge on a program (mail, phone or SMS) I will check it anyway, so I don't need the full info on the home screen.