What are the reasons to learn different algorithms / data structures serving the same purpose?

I have been wondering about this question since I was an undergraduate student. It is a general question but I will elaborate with examples below. I have seen a lot of algorithms - for example, for maximum flow problems, I know around 3 algorithms which can solve the problem: Ford-Fulkerson, Edmonds-Karp & Dinic, with Dinic having the best complexity. For data structures - for example, heaps - there are binary heaps, binomial heaps & Fibonacci heaps, with Fibonacci heap having the best overall complexity. What keeps me confusing is: are there any reasons why we need to know them all? Why not just learn and get familiar with the best complexity one? I know it is the best if we know them all, I just want to know are there any "more valid" reasons, like some problems / algorithms can only be solved by using A but not B, etc.