What is the value of using i instead of a more specific variable name? To save 1 second or 10 seconds or maybe, maybe, even 30 seconds of thinking and typing?
What is the cost of using i? Maybe nothing. Maybe the code is so simple that using i is fine. But maybe, maybe, using i will force developers who come to this code in the future to have to think for a moment "what does i mean here?" They will have to think: "is it an index, a count, an offset, a flag?" They will have to think: "is this change safe, is it correct, will I be off by 1?"
Using i saves time and intellectual effort when writing code but may end up costing more intellectual effort in the future, or perhaps even result in the inadvertent introduction of defects due to misunderstanding the code.
Generally speaking, most software development is maintenance and extension, so the amount of time spent reading your code will vastly exceed the amount of time spent writing it.
It's very easy to develop the habit of using meaningful names everywhere, and once you have that habit it takes only a few seconds more to write code with meaningful names, but then you have code which is easier to read, easier to understand, and more obviously correct.
