One correlated but ancillary benefit, is that there are fewer variables to simulate the state for in your brain, while you're reading the code. You don't have to wonder if a variable is going to change on you, in-between when it is initialized and when it is used.
It's safer still to use a library (e.g. urllib3) that does encoding for you (allowing you to omit magic strings like `"%7C"` from the logic of this function alltogther).
Like GP said, very handy for one-off scripts or areas of your codebase where quality is "less important". I may be pedantic, but I wouldn't give this a pass on code review.