Right now the app injects most services so site plugins can use them. This can have an impact on performance, and in general it doesn't make much sense that a plugin can access the functionalities of a certain activity.
The only exception are subplugins. E.g. accessrules plugins should have access to the quiz services because they're a quiz subplugin.
After this change, if a plugin still needs to do something with a certain activity they can always replicate the code in their JS.
This would be the first step towards something that we've wanted to do for a while: decrease the number of services/functions injected to plugins, and have more control over it. This isn't only a problem in performance, it also makes it harder to maintain the code because any change in those services can potentially break plugins.