I remember when I had my 2008 MacBook Pro, I waited 6 weeks to get an SD card reader for the ExpressCard slot from China. Though to use it, you'd have to take it out and put it back in each time, I was still really happy that I didn't have to use an external card reader to hog up my 2 USB ports anymore. Then the next release of the machine had the SD card reader built in, and I though to myself that Apple is really smart, doing exactly what I needed. I use the card slot every day.
For the 2008 machine I also had to get a VGA adapter, because the computer only had DisplayPort. I took it with me everywhere because I did lots of presentations. No projector had a DisplayPort. It was a hassle and people kept borrowing it and not giving it back. Anyway, the next machine had a built in HDMI port. Wow, again, Apple doing the right thing, it's so practical, I use it all the time!
What I find strange is that Apple often does something great, but it only lasts a few years. They then step back and remove the cool feature as if it was no longer a good idea after all. You'd think that once you've achieved something that proved useful and welcome in tech, it would remain that way.
Why exactly are thinner computer better? Oh, to be more convenient, more portable, lighter, easier to carry, right? Now the thing with adapters is that they're less convenient, they're not travel friendly because you forget them and lose them, they make taking your computer with you a hassle because you can't just take 1 device and be set. Making the computer slightly thinner doesn't make up for that.
Add to this that the computer is far more expensive than the previous one, and requires these ridiculously expensive adapters (and maybe not just one of them!).
Maybe in 3-4 years every cable will be a USB-C cable, and Apple is helping push this forward. But it sure isn't going to be fun until then.
The computer of the future is quite a pain in the ass if you're using it in the present.