...but why. about all of this. I mean, beyond the "oh cool, I can do a thing".
The way I see it.
Originally the only big screens people had were TVs. They only took RF and composite/scart in.
Minicomputers had long since died and trying to get your PC (which could do all this cool stuff) into one of those was hard.
Up rocks the likes of the xbox*, which was pretty cheap for what it was, and gets hacked and being essentially a PC gets all sorts of cool things made for it. Emulators, video watching (ever tried to use one of those MPEG4 DVD players?) and cool stuff people made just because and would never be viable for homebrew all happened. Some people seem to be in a hurry to forget the last thing ever happened and think homebrew = emulators, no doubt it was popular but I feel genuinely sorry for those people.
Around the same time handhelds also represented a really nice way to have a portable programmable screen** with some inputs and computing power.
http://reinerziegler.de/GBA/gba.htm#great GBA hardware for some of the things. The DS and PSP also offering a full network stack and some reasonable power. A few people had tried to make phones of some power and programmability before the iphone came along but it was not going to happen (far too restricted, or possibly far too Japan centric) and j2me stuff was definitely a product of its time.
*there was some homebrew on older things (it tending to be called PD/public domain back then), however it was the GBA and xbox that really kicked it off.
Android and IOS then changed everything, not all for the better (I still resent not having root by default), but it changed the game entirely, as readily available money is wont to do and it is not going anywhere. PC demands also stagnated (a core2 machine could well be over a decade old and still represent a viable machine for everyday use) and prices dropped, not to mention screens gained HDMI and VGA to match PCs. Plug computers also got usefully powerful and then stuff like raspberry pis happened.
**I recall about 13 years ago being in a computing room in the electrical engineering department of a university. On the wall were all these posters saying look at this company called ARM and all the things they power you did not know about. Today having some drooler in the phone shop actually know the difference between two different ARM chips of the same line is then staggering to me when I think back.
In some ways I reckon many got stuck in the previous era and think it can happen again. The pitful showing on the 3ds saying how laughable I think that notion is. If not that then they are about the devices, I hold however that devices are a means to an end and not the end goal and I am still very much about having cool things nobody in either sales, marketing or legal could see being released.
At the same time people quite like if not a dedicated device then one they can set to a task and not really be down a device, maybe one day we will have universal computing (have you ever been on your PC and picked up your phone to do something? You have then suffered a failure of computing user interfaces) but given we can't even sort instant/text messaging out I am not expecting much any time soon. Or if you prefer then remove my PC from me and I am troubled, take one of my raspberry pis and twist it to do what you want before having it back a few hours later and it is all good. Being able to rock up at your friends, drop the switch in a device, play some games and then watch a film you downloaded (you know Nintendo is never going to provide a nice MKV demuxer that you can swap subs, languages and more about on) is cool.
That alone is also but one part of why I find the "but I already have a phone" argument so weak. Equally were I a funnier man we would cue up some
imagine and I would find the "android is a bad plan" set talking in the switch potential threads.
I don't know that we will be seeing people buying Switches to turn into media boxes like we saw with the original xbox (or PS2 and PS3 for DVD and blu players respectively, and possibly an xbone for some of the streaming stuff), and I don't know that we will be having people buy one like they might have got a DS to SSH into machines (it happened). We might however see some kids picking one up as their private computing device (it is just games after all) as PCs have long been locked down and plenty of parents are wise to phones and tablets.
For another thing out there to consider. While the likes of the GBA, DS and PSP were nice they were more just acceptable power than comfortably powered. To make the most of them you did need fairly good coding skills, and there were serious benefits to having outright great ones (all those lovingly hand crafted emulators, with all the nice features, something the 3ds did not have really). Android then allows someone that can fumble their way through eclipse to generate something cool, especially if they can take some nice web api and write a wrapper for it.
So yeah the Switch is in a tenuous position in homebrew terms. Android is instant library, lower barrier to entry, gives the big boy devs a chance to earn some money which retains/attracts them and helps with the "disposable" device thing. I then struggle to see downsides.