When you load test, you want to know exactly who is hitting the site and what frequency. That is why they develop test plans. To determine weakness and failures and where they might happen. If people are allowed to randomly hit the site, then no clear metrics can be obtained. They have automated load testers that can hit the site programatically at the same time.
No you would not depending on the testing you are doing. They may want to do load by feature, then an all in one. Load testing is a vague term used to describe many different stress, load and performance scenarios.