My impression is that historians are about the reading of contemporary material, and drawing conclusions from that material; a realisation I came to writing this is that historians seem to have the same sense of wonder and passion for historical minutiae as I have for nature and science. I remember talking to a historian of science who was working on an original manuscript of some important scientific work, it quickly become clear that this was much more exciting for her than me. To me the exciting thing was the theory presented in it's modern form, I wasn't very interested in the original.
And that's not to mention the real contemporary material: correspondence, notes and labbooks. I have a sequence of about 20 labbooks in the loft from 15 years of research, supplemented by a hoard of files and e-mails stored on my computer, covering the same period. I'm not sure I even want to try to reconstruct what I was thinking over that period - let alone try it on someone else's records! It's not that I'm remiss as a scientist, we just don't read original material.
The original presentation of an idea may not be the clearest, and it may well be that it makes more sense later to present it as part of a larger whole, and to be honest scientists can be a bit hit and miss: Newton's physics is great but the alchemy was bonkers. Science comes in bits, these days the bits are the size of a journal article and it's only when you're doing active research at the cutting edge that you need to keep track of the bits.
Mathematical notation is an issue for original publications. For example, Maxwell's equations, which describe electromagnetism (radio waves, electricity, light...) are a monster in his original presentation but can be squished down to four short lines in modern notation (actually a notation introduced not long after his original paper). There's a rule of thumb that each equation in an article halves the number of readers, therefore I link you to Maxwell's 1865 version on page 2 of this document with the modern version at the bottom of page 6...
A bit of history is introduced into the teaching of science but it's either anecdotal such as the apple falling on Newton's head, Gallileo dropping things off towers, Sadi Carnot and his wacky exercises, or we might give a quick historical recap as we introduce a subject. But to be honest it's really all window dressing, the function of this history is to provide a little colour and give students the opportunity to do some exercises which are tractible.
Are scientists losing out as a result of this historical blindness? History should certainly inform us of our place in society, and our future place in society (okay - I'm talking about cash here!). I'm less sure that it has something to teach us on the 'craft' of science, this is something that comes from professional training - perhaps it would help if we were not presented with such caricatures of our scientific heroes.
So that's my view, how wrong can I be?