If I go for simplicity, I can write code like this:
10000000000000000000000000000000000000000000
But if I go for readability, I will prefer this:
1e43
On the other hand, 1000 is much more readable and simple than 1e3 unless you work with numbers in scientific notation all the time.
This is a degenerate example of much more general pattern you can find almost anywhere -- copying something is simple, but can quickly become unreadable/inefficient/bad in a lot of different ways. Generalizing and reusing, on the other hand, is harder at first ("wtf is e?! did they mean to write 1343?" someone might say), but can help a lot in a long run.