Is pile-shuffling useful?

I posit that it is not, and here's my argument.

"Pile-shuffling" is the method of distributing the cards into a number of piles, and then just collecting the piles together. This is rather different from the traditional "mash shuffling" and "riffle shuffling" methods.

This is an important fact: Pile-shuffling does not evenly randomize your deck. This might sound like something self-evident and trivial, but nevertheless surprisingly many people have all kinds of misconceptions about it. Some people believe that pile-shuffling two times into a different number of piles is "sufficient randomization". Many even mention prime numbers (even though they have nothing to do with how randomized the deck will become.) Pile-shuffling does not evenly randomize your deck even if you put each card on a random pile.

Assume that at the end of a game you simply collect all your lands and put them on top of your library, and then pile-shuffle for example into seven piles. This means that you know that each 8th card in your deck will be a land. This is obviously not even randomization. Even if you couldn't tell which land will come after the next seven cards, it's still not randomized because you know for certain that it will be a land. This ought to be pretty obvious.

Moreover, if you did this, it would be effectively mana-weaving (ie. deliberately distributing your lands evenly in your deck, with no randomization afterwards), which is illegal.

Most players who pile-shuffle will mash-shuffle or riffle-shuffle extensively afterwards, and they argue that this is sufficient randomization which nullifies the "mana-weaving", and therefore it's not cheating. And that's the crucial point: If they are going to sufficiently randomize it afterwards, undoing any ordering that the pile-shuffling achieved, then the pile-shuffling was a complete waste of time because it did nothing useful.

Pile-shuffling does not increase the randomness of the deck (by its very nature), and the deck is going to be randomized afterwards anyways, so why exactly do it? What's the use?

Some may ask "why not? What's the harm?" There's no other harm except that pile-shuffling takes time, and thus it's a complete waste of it. So why waste time on a procedure that achieves nothing useful?

Some people argue that pile-shuffling is useful to count your cards (in order to verify that no card ended up in the wrong place during a game, and that there aren't any extra cards). Ok, that's fine. However, especially tournament players often pile-shuffle several times. These extra shuffles do not have even this excuse.

The main reason why people pile-shuffle is because they feel that normal mash-shuffling doesn't "separate" cards enough from each other. They feel that pile-shuffling separates the cards from each other in the deck, and thus increases randomness and evens out the deck more (especially in terms of land distribution). But this is once again borderline mana-weaving: If you feel that your mash-shuffling is not randomizing the deck enough, and thus you feel the need to pile-shuffle to compensate, then you are borderline mana-weaving, ie. borderline cheating. If you argue that your mash-shuffling is enough to randomize the deck afterwards (and thus undo any possible mana weaving), then you are arguing that the pile-shuffling was indeed useless and a waste of time.

I find it curious how defensive people get when these things are brought up. Many, if not most, players will vehemently defend pile-shuffling no matter what arguments against its usefulness are presented. I have yet to find a player that simply agrees.

(Often the conversation will quickly start going in circles. When you argue that pile-shuffling effectively amounts to stacking/manaweaving your deck, they will argue that the mash shuffling afterwards will undo any such stacking. When you then point out that they just confirmed that the pile-shuffling achieved nothing useful because of the mash shuffling, they will insist that it was useful because it separates clumps of lands etc. In other words, you can point out, they are indeed stacking/manaweaving with the pile shuffling. And in circles the conversation will go...)

If you don't think pile-shuffling is all that slow, watch this video. (Note that the several pile-shuffles the player does eg. starting at 2:25 in the video have zero benefit in terms of deck randomization because of the rather massive amount of mash shuffling done in addition to them.)