Storage is not the issue. Indexing and retrieval is the problem.
If the concept is that I should keep everything so I don't forget my mistakes, how exactly am I supposed to index and later retrieve my mistakes?
If I am going to go out tomorrow and photograph butterflies, is the intention for me to retrieve potentially hundreds of my lousy butterfly photographs and look at them and glean exactly what?
Personally, I don't have a problem remembering my photographic mistakes. What I have a problem with is determining in the field, at the spur of the moment, how to prevent my mistakes.
In the "information age" (what ever that means), it is easy and cheap to store data. Storing is not the problem. Technology takes care of that. But not as many people are working the much more harder issues of indexing and retrieval.
It is all well and good to proclaim "save everything". Especially since you saving everything you have does not cost me anything. But unless you put in some serious effort into indexing, all you will have is a large box o' data to sift through.
My personal workflow is to
1. Immediately cull the obvious bad shots that really can't be fixed. These include just poor technique on my part.
2. Get rid of duplicates i.e., multiple shots that really don't add anything specific from the other shots.
This usually gets me down to about 10%
Then I can really start culling down the technically competent but boring shots.
So I end up with about 1% which is pretty good for me.
I tend to save those 1% shots and never look at them again.