It's just another type of input, there's distinct advantages and disadvantages to all of them. None of them will ever obsolesce another. Apple's extreme stance on keeping things as simple as possible pushed the market for a long time, but things are starting to swing back around now that bringing back the inputs of yesterday appears to be the only way to separate a product from all the others. I'd like to see trackballs and spinners (like on Tempest) make a comeback too.
Keep in mind that to Apple, this is for accessibility. The mouse pointer and associated protocols are very important for some assisted computing devices.
The real whole point of touch-based devices was to redefine the meaning of a personal computer so that it can be locked down and under control from the device makers, forcing artificial limitations towards their users under the pretense of usability and security.
The keyboard and mouse stuff was just cherries on top and quite rotten cherries at that.
That doesn't make any sense considering there are plenty of touchscreen devices that aren't locked down.
It makes perfect sense considering the vast majority of touchscreen devices are locked down. Also a hint: if you ever thought that the ability for "sideloading" means that a device is not locked down, you have fallen victim to PR-speak even though that very word is an indicator of how they see that ability: something not normal, but something that happens from the side. This sort of speech, changing the normal "installing" to mean something controlled by the vendor of your OS and renaming the previous "installing" to "sideloading" (which is optional and this sort of ability to disable it is condoned by the OS maker) is affecting the way people even think about these devices.
It made it possible not to need one.
That doesn't mean it can't ever be beneficial to have support for one.
Try to do a spreadsheet, or just write up a document, on a touch screen.