[Quoth]

I regard them since 17th C as publisher egotism. You don't need them for a chapter or section start, because changing indent and top margin and prior heading does that. They also break up the first word and reduce reading comprehension.

Seeing then as I don't approve of them on paper I'd never implement them in an ebook and if I'm having to edit a book for other reasons I'll remove all drop cap styling. Easier taken out than fixed.

Edit:
Similarly the practice of using SMALL CAPS at the start of the paragraph at a new section is historic and now simply adds unwanted complexity and slows reading. Traditionally they are not even simply smaller caps, but a related face.