I don’t think there are any trends for ergonomics. If it’s a trend then its more of a styling preference.
Just because it’s been done that way for years doesn’t mean its right. A lot of innovations or improvements are done when you start from scratch disregarding existing designs. Have you tried opening a couple of them up? See what’s inside? You’ll notice why they made some decisions.
Drills & drivers are used in very awkward ways so the best you can do (other than provide an adjustable angle handle) is to provide a standard starting angle. In theory you should apply pressure straight and from behind the bit in order to not go at an angle.
Maybe make your own prototype and play with the angles and have other people use it while you watch. Or simply get 3-4 different drills with different angle and see what people do and how they twist their hands during use.
Some of the changes may be due to smaller and lighter components. Mainly the battery. Have you research some corded electric drills?