Under statistics, you can do a sample draw, and see the next few cards.

This is handy for a quick RNG test, however you can mulligan but not reshuffle the library.
Sometimes I see fetch cards in my hand and it would be nice to quickly see how the first 3 turns my pan out if I choose to reshuffle the library.

Request to add a link/button that keeps your hand but reshuffles the library.

For all statistical purposes, it is essentially the same as if you didn't shuffle your library. You can play it out in your head like your next cards used to be some other cards, but you already reshuffled and the cards you see are the cards you would get after shuffling.

Its all the same (at least statistically), unless you have Brainstorm or some other way of peeking into your library.