Most free software licenses don't concern themselves with use, except that they may make it clear that use is not restricted in any way. A license that restricts use in any way is probably not free.

> you are not entitled to be given access to the source code.

If you're the user of a binary image someone spun from a GNU licensed program, actually you are entitled to that, if it is the Affero license (AGPL), you may be entitled to source code access even if you just use the thing as an online service. Specifically, you're entitled to access to the source code of the modified version that you're actually using.

> If you _use_ open source code (ie. as part of your product), you may be _required_ to also provide source code, attribution etc.

That's redistribution. If you redistribute some kinds of open source code in a product, you may have to provide source code, and that's even if that code is never called. The presence of that code in the image is the key thing, not whether it is used. Use occurs on the target system, by the end user.