Cover Letters - Do you read them? Are they worth it?

TLDR: Do you read cover letters? Do you find them useful?

I work at a boutique investment bank and I love that being part of a small team I get so much exposure to the entire deal for example I am completely responsible for all the modelling which I really enjoy as I feel i gain a much greater understanding of businesses than when I am just putting together a teaser or CIM. The flip side of this is it means you also have to do a lot of the less enjoyable tasks for example I am currently sat here reading through a tonne of cover letters and I was wondering what other peoples opinions are about cover letters? Do you find them useful? Did they help you to get a job? They seem to be such a bad investment in time considering how long they must take people to write and then for most likely the majority of people just to ignore them. At least my experience when I was job seeking was that I felt no one had ever read mine.