FOUR cameras, however!

It's intentional. They'd like to drop features to cut on design and manufacture costs, while taking out features most of the target audience doesn't really care about. Some of these are just greedy. Phones used to rely on microSD expansion, but once you drop this option you could charge for additional space much more than what the equivalent microSD card would cost. You can also stop shipping phones with chargers because most people have them anyway. This is pure profit as the customer is paying the same price, but doesn't get a charger.

As for other features, they probably dropped them because people just didn't care enough.

It seems to be incredibly difficult to design a phone from scratch, and that's why we only see a handful of manufacturers, with the small endeavors being able to make something that looks obsolete by the time it rolls out and even then it takes a few months to overcome all the bugs and glitches. Fairphone is the closest we've got, but it's still far off and strays further with each generation.