The surest way to lose a customer is to tell them they don't need to know something.
We've run into a lot of "tire-kicking" customers, but we try to take the time to explain what we install on our server and why.
And if we don't know why something is installed on the server, we learn why. In fact I don't believe you should have anything installed on your server unless you know why it's there. Any other attitude is going to leave you open to severe problems with hackers, crackers, and the like. At least imho.
We've had customers with special needs, and we've always tried to fill those special needs; it keeps customers loyal. Of course sometimes we've had to tell the client they needed their own system, that we just can't do something on a shared system.
When that happens we tell them why, and the answer is never "because that's how we do it"; we always try to help them understand the decision we made and the security and resource tradeoffs that help us make our decisions.
Sometimes we even revisit a decision based on a client's request for information or for a specific module or compile option. After all, most of us are not the largest of webhost companies; if we can't give our customers personal attention, then there's little reason for them to buy from us.