The True Purpose Of The "Pikaclones"?

Every Pokemon generation after the second has had a new electric rodent Pokemon that is not in Pikachu's evolutionary line. Why is this? Is GameFreak merely trying to recapture the success of Pikachu each time? While that is probably part of it, I feel that there is more to it than that. I think most of the so-called "Pikaclones" is actually meant to show off something about the generation they are introduced in. For the purposes of this post, whether or not these Pokemon suck like a high-powered vacuum cleaner will be ignored.

Gen III: Plusle and Minun
So, the third Generation of Pokemon games introduced Double Battles and Abilities, among other things. Plusle and Minun's Abilities, "Plus" and "Minus" respectively, would only activate if Pokemon with both were out at the same time on the same side, which could only happen in a Double Battle. Later generations changed things around so that more Pokemon could have either "Plus" or "Minus", as well as making it so the Ability will activate if a Pokemon with either is teamed up with a Pokemon that has one or the other.

Gen IV: Pachirisu
Um...well, I said "most", didn't I? I mean, I guess learning Spark, a physical Electric-type move, counts, since Generation IV made it so a move being Physical or Special did not depend on the move's type?

Gen V: Emolga
So, Emolga was introduced in a Generation where GameFreak did some interesting things, such as emphasizing the story more than in previous Generations, only allowing the player to catch newly-introduced Pokemon until the post-game (until Black 2 and White 2, that is), and shoving plenty of features into a now-defunct Flash site. To reflect this, the "Pikaclone" of Black and White has a relatively unique type, Electric/Flying, which at the time was only shared by Zapdos, Fan-Rotom (as of that Generation), and Thundurus. Zapdos and Thundurus are Legendary Pokemon, and Rotom's non-Electric type can change, so Emolga was, and in fact still is, the only non-Legendary to be a dedicated Electric-Flying type. In a Generation that took a unique direction, the "Pikaclone" was, itself, rather unique.

Gen VI: Dedenne
One element Generation VI introduced was the Fairy type. Dedenne is part Fairy type. For some reason it did not get a Mega Evolution despite the mechanic being introduced here as well. It should be noted that the "Attempting to recapture the appeal of Pikachu" aspect of "Pikaclones" is plain as day here, as Dedenne looks very much like Pikachu did before it was redesigned.

Gen VII: Togedemaru
So, this is kind of a stretch, but, with one major exception, every Pokemon introduced in Generation VII has a low Speed stat compared to those of earlier Generations. The intent is arguably for Alolan Pokemon to be played with a more defensive playstyle, which is certainly shown with Togedemaru, an Electric-Steel hedgehog that learns the move Spiky Shield. While Togedemaru is not the first Pokemon to be able to know Spiky Shield, it is not exactly a common move.

So, as stated at the beginning of this post, most of the "Pikaclones" exist to show off something about a particular Generation. When the people at GameFreak want to point out something about a new Pokemon Generation, they'll probably make a Pokemon that happens to be an electric rodent in order to show it off.