The times they are a changing and with the world getting more and more security conscious you will see more and more cases where passports are required.
If you forsee yourself traveling outside the country in the future getting a passport is a good idea. If
DCL is a one-shot deal for you, its probably not necessary.
If there is anything unusual about your birth certificate then get a passport so that all the issues are dealt with up front.
Examples:
You were born a US citizen to US parents but out of the country.
Your birth certificate is very worn and cannot be easily replaced.
There is a significant difference between the name on your birth certificate and the name on your identification. Such as you've had your name legally changed etc.
Basically if you have any concerns at all that your birth certificate may be questioned for any reason, I would recommend getting a passport.
If your birth certificate has the proper seals, is readable, is from within the US and the name matches (married name being the exception) than its not needed.