Try to shoot a 4K video that's longer than 5-10 minutes and then tell me extSD cards are no longer needed. Especially if you've only got a 16 or 32GB device to start with. Having the ability to pop in a new card and continue shooting is a great feature. Especially if you have spotty coverage which prevents you from quickly uploading it to the cloud.
Rumors have already started that point to Samsung putting an extSD card slot in the upcoming S7. The people have spoken and Samsung is listening. Sure, those that have never had the option to begin with, have dealt with it just fine, but that still doesn't negate the convenience of it all.
We shall see if they "listen" to the vocal minority... Until 4K TV's are the norm, I don't see a lot of people caring about taking 4K video over 1080p...
I think that we enthusiasts get a false sense of "normal" from these forums.
The average consumer doesn't know what a bootloader or root are, what they do, or even know that they exist. All the things that people get worked up into a tizzy over here and on XDA, are the 0.025% of the phone market that are nerds and get all tingly in their boxer shorts over specs. Most people don't know, and don't care, and they buy a lot more phones than we do.
We are not seeing flagship phones coming with 8-16gb any more. Most start at 32gb, and are now going to 64gb and up.
Apple has NEVER had SD slots on their phones, and that doesn't stop them from selling a gazillion of them each year, does it? Do people with iPhones not take pics or videos?
Even for people that do take 4k videos, which I submit to you is very rare among the general population... how many need to store them on their phone?
And "just slapping in a new card" oftentimes requires you to power the phone down, remove your protective case, remove the back plate, sometimes pop out the battery to get to the slot, then swap them and put it all back together and reboot,,,
Frankly, not all that convenient... I see most people taking videos and then downloading them off to a PC or laptop via USB.
What would be ideal, is just to have an OTG cable to to a little portable HD in your pocket and just save stuff to that if you really need to video a 25 minute wedding ceremony at full 4k...