Comment by lopatin

Nike: Just do it.

OP: Well it's not always as simple as that. How will you get to the gym? Will you drive or ride a bike? What if there are other people using your usual weight machines, do you wait or do cardio? If you're working out after work, will you need to bring a change of clothes? How will my diet affect my workout? And how can I track my fitness to ensure I'm making progress?

Sometimes the answer is to just inject that JavaScript snippet. Of course all the follow up questions that OP mentioned to injecting that JS snippet are valid. But that is part of the "just". The person "just"ing that has assumed that you will consider all of those caveats and there should be no issues, because after all, why would there be if millions of people already use it without issue? It's up to the engineer to just do it, or push back if it's not actually as simple as it seems.