Your DNS server dies. You rebuild it because you know how. Cool, right? You need to compile the newest version of BIND and install it, and you do it because you know how, right? When the monitoring system reports that error that happens now and then, you know how to fix it, right? You know how to do all this. Why write anything down?
Will you remember how to do these things 6 months from now? I find myself having to re-invent a process from scratch if I haven't done it in a few months (or sometimes just a few days!). Not only do I re-invent the process, I repeat all my old mistakes and learn from them again. What a waste of time.
Will you remember how to do these things when the pressure is on? My memory works worse during an emergency.
What about when you aren't around? How can you take a relaxing vacation if you feel burdened? You can't complain to be over-worked and unable to share your work with others if you haven't created a way to share the workload.
What about new people on the team? Should they learn how to do these things by watching you do it or can they learn on their own? If they can learn on their own and only bother you when they get stuck it saves you time and makes you look less like the information hording curmudgeon that you don't want to be. In fact, it makes people feel welcome and included if their new team has these kind of tasks documented.
How can your manager promote you or put you on a new and more interesting project if you are the only person with certain knowledge?
Each service should have certain things documented. If each service documents them the same way, people get used to it and can find what they need easier. I make a sub-wiki (or a mini-web site, or a Google Sites "Site") for each service:
Each of these has the same 7 tabs: (some may be blank)
If this is something being developed in-house, the 8th tab would be information for the team: how to set up a development environment, how to do integration testing, how to do release engineering, and other tips that developers will need. For example one project I'm on has a page that describes the exact steps for adding a new RPC to the system.
Be a hero and create the template for the rest of your team to use. Document a basic service like DNS to get started. Then do this for a bigger service. Create the skeleton so others can use it as a template and just fill in the missing pieces. Get in the habit of starting a new opsdoc any time you begin a new project.